U.S. patent application number 15/762399 was filed with the patent office on 2018-09-20 for build plate assemblies for continuous liquid interphase printing having lighting panels and related methods, systems and devices.
The applicant listed for this patent is CARBON3D, INC.. Invention is credited to Gregory W. Dachs, II, Bob E. Feller, Ariel M. Herrmann, David Moore, John R. Tumbleston.
Application Number | 20180264724 15/762399 |
Document ID | / |
Family ID | 63520932 |
Filed Date | 2018-09-20 |
United States Patent
Application |
20180264724 |
Kind Code |
A1 |
Feller; Bob E. ; et
al. |
September 20, 2018 |
BUILD PLATE ASSEMBLIES FOR CONTINUOUS LIQUID INTERPHASE PRINTING
HAVING LIGHTING PANELS AND RELATED METHODS, SYSTEMS AND DEVICES
Abstract
A build plate assembly for a three-dimensional printer includes:
a lighting panel having individually addressable pixels configured
to selectively emit light and/or transmit light from illumination
below the pixels to a top surface top surface of the lighting
panel; a rigid, optically transparent, gas-impermeable planar
screen or base having an upper surface having an uneven surface
topology and a lower surface that is affixed to the top surface of
the lighting panel; and a flexible, optically transparent,
gas-permeable sheet having upper and lower surfaces, the upper
surface comprising a build surface for forming a three-dimensional
object, the sheet lower surface positioned opposite the base,
wherein the build plate is configured to permit gas flow to the
build surface.
Inventors: |
Feller; Bob E.; (San Mateo,
CA) ; Herrmann; Ariel M.; (San Francisco, CA)
; Tumbleston; John R.; (Menlo Park, CA) ; Moore;
David; (San Carlos, CA) ; Dachs, II; Gregory W.;
(San Mateo, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CARBON3D, INC. |
Redwood City |
CA |
US |
|
|
Family ID: |
63520932 |
Appl. No.: |
15/762399 |
Filed: |
September 23, 2016 |
PCT Filed: |
September 23, 2016 |
PCT NO: |
PCT/US2016/053421 |
371 Date: |
March 22, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62262783 |
Dec 3, 2015 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B33Y 30/00 20141201;
B29C 64/135 20170801; B29C 64/393 20170801; B29C 64/245 20170801;
B33Y 50/02 20141201; B33Y 10/00 20141201 |
International
Class: |
B29C 64/245 20060101
B29C064/245; B29C 64/135 20060101 B29C064/135; B29C 64/393 20060101
B29C064/393; B33Y 10/00 20060101 B33Y010/00; B33Y 30/00 20060101
B33Y030/00; B33Y 50/02 20060101 B33Y050/02 |
Claims
1. A build plate assembly for a three-dimensional printer
comprising: a lighting panel having individually addressable pixels
configured to selectively emit light and/or transmit light from
illumination below the pixels to a top surface top surface of the
lighting panel; a rigid, optically transparent, gas-impermeable
planar screen or base having an upper surface having an uneven
surface topology and a lower surface that is affixed to the top
surface of the lighting panel; a flexible, optically transparent,
gas-permeable sheet having upper and lower surfaces, the upper
surface comprising a build surface for forming a three-dimensional
object, the sheet lower surface positioned opposite the base,
wherein the build plate is configured to permit gas flow to the
build surface.
2. The build plate assembly of claim 1, further comprising an
adhesive layer between the gas-permeable sheet and the base, and a
channel layer defining channels therein.
3. The build plate assembly of claim 1, wherein the channel layer
comprises a permeable material comprising a permeable polymer.
4. The build plate assembly of claim 1, wherein the channel layer
defines channels on a bottom surface opposite the adhesive.
5. The build plate assembly of claim 1, wherein the channel layer
is adhered to the base by chemical bonding.
6. The build plate assembly of claim 1, wherein the adhesive layer
comprises a gas-permeable adhesive.
7. The build plate assembly of claim 1, wherein the adhesive layer
comprises a poly(dimethylsiloxane) (PDMS) film.
8. The build plate assembly of claim 1, wherein the base comprises
a top portion and a bottom portion, wherein the top portion
comprises a patterned rigid polymer that provides the surface
topology and the top portion is adhered to the bottom portion.
9. The build plate assembly of claim 8, wherein the top portion
comprises a first material and the bottom portion comprises a
second material that is different from the first material.
10. The build plate assembly of or claim 9, wherein the second
material comprises sapphire, glass and/or quartz.
11. The build plate assembly of claim 1, further comprising an
elastomeric layer between the channel layer and the base configured
to increase an elasticity of the build surface.
12. The build plate assembly of claim 1, wherein the permeable
sheet and/or channel layer comprises a PDMS composite comprising
fluorescent, oxygen-sensing particles for sensing oxygen.
13. The build plate assembly of claim 1, wherein the permeable
sheet, elastomeric layer and/or channel layer comprises a PDMS
composite comprising electrically conductive particles for heating
a portion of the build plate.
14. The build plate assembly of claim 1, wherein the lighting panel
comprises a LCD panel.
15. The build plate assembly of claim 1, wherein the lighting panel
comprises an OLED panel.
16. The build plate assembly of claim 1, wherein the lighting panel
comprises an ultraviolet LED light source array.
17. The build plate assembly of claim 1, wherein the lighting panel
is a grey scale lighting panel.
18. The build plate assembly of claim 1, further comprising light
guides in the build plate that correspond to the individually
addressable pixels of the lighting panel.
19. The build plate assembly of claim 1, wherein the surface
topology comprises random or patterned features configured to
maintain a predefined gap between the planar base and portions of
the gas-permeable sheet
20. The build plate assembly of claim 1, wherein the gas-permeable
sheet includes a thickness, and the gap is less than or equal to
five times the thickness of the sheet.
21. The build plate assembly of claim 2, wherein a region between
the planar base and the gas-permeable sheet comprises gap regions
between the planar base and the gas-permeable sheet in which a gap
that is sufficient to increase gas flow and reduce an area of
wetting on the gas permeable sheet is maintained.
22-27. (canceled)
28. The build plate assembly of claim 1, wherein the surface
topology comprises depressions or protrusions having a diameter of
about 1 to about 10 .mu.m.
29. The build plate assembly of claim 1, wherein the surface
topology that increases gas flow to the build surface is on the
base upper surface.
30. The build plate assembly of claim 1, wherein the surface
topology that increases gas flow to the build surface is on the
sheet lower surface.
31-33. (canceled)
34. The build plate assembly of claim 1, wherein the surface
topology has an optical scattering angle of less than 20%.
35. A method of forming a three-dimensional object, comprising:
providing a carrier and an optically transparent member having a
build surface, said carrier and said build surface defining a build
region therebetween; filling said build region with a polymerizable
liquid, continuously or intermittently irradiating said build
region with light through said optically transparent member to form
a solid polymer from said polymerizable liquid, continuously or
intermittently advancing (e.g., sequentially or concurrently with
said irradiating step) said carrier away from said build surface to
form said three-dimensional object from said solid polymer, wherein
said optically transparent member comprises a build plate
comprising: a lighting panel having individually addressable pixels
configured to selectively emit light and/or transmit light from
illumination below the pixels to a top surface top surface of the
lighting panel; a rigid, optically transparent, gas-impermeable
planar screen or base having an upper surface having an uneven
surface topology and a lower surface that is affixed to the top
surface of the lighting panel; a flexible, optically transparent,
gas-permeable sheet having upper and lower surfaces, the upper
surface comprising a build surface for forming a three-dimensional
object, the sheet lower surface positioned opposite the base,
wherein the build plate is configured to permit gas flow to the
build surface.
36. The method of claim 35, wherein said filling, irradiating,
and/or advancing steps are carried out while also concurrently: (i)
continuously maintaining a dead zone of polymerizable liquid in
contact with said build surface, and (ii) continuously maintaining
a gradient of polymerization zone between said dead zone and said
solid polymer and in contact with each thereof, said gradient of
polymerization zone comprising said polymerizable liquid in
partially cured form.
37. The method of claim 35, wherein the carrier with said
polymerized region adhered thereto is unidirectionally advanced
away from said build surface on said stationary build plate.
38. The method of claim 35, said filling step further comprising
vertically reciprocating said carrier with respect to said build
surface.sub.s to enhance or speed the refilling of said build
region with said polymerizable liquid.
39. The method of claim 38, wherein said vertically reciprocating
step comprises an upstroke and a downstroke, with the distance of
said upstroke greater than the distance of said downstroke, to
thereby concurrently carry out said advancing step in part or in
whole.
40. The method of claim 35, wherein said vertically reciprocating
step comprises, an upstroke, and wherein the speed of said upstroke
accelerates over a period of time during said upstroke.
41. The method of claim 40, wherein said upstroke begins
gradually.
42. The method of claims 35, wherein said vertically reciprocating
step comprises a downstroke, and wherein the speed of said
downstroke decelerates over a period of time during said
downstroke.
43. The method of claim 42, wherein said downstroke ends
gradually.
44. The method of claims 18, wherein said vertically reciprocating
step is carried out over a total time of from 0.01 seconds up to 10
seconds, and/or over an upstroke distance of travel of from 0.02
millimeters to 10 millimeters.
45. The method of claim 18, wherein said advancing is carried out
intermittently at a rate of 1 individual advance per minute up to
1000 individual advances per minute, each followed by a pause
during which an irradiating step is carried out.
46. The method of claim 28, wherein each of said individual
advances is carried out over an average distance of travel for each
advance of from 10 microns to 200 microns.
47. The method of claims 18, wherein said build surface is fixed
and stationary in the lateral (e.g., X and Y) dimensions.
48. The method of claims 18, wherein said build surface is fixed
and stationary in the vertical (or Z) dimension.
49-51. (canceled)
52. The method of claim 18, wherein said gradient of polymerization
zone is maintained for a time of at least 5 seconds.
53-56. (canceled)
57. An apparatus for forming a three-dimensional object from a
polymerizable liquid, comprising: (a) a support; (b) a carrier
operatively associated with said support on which carrier said
three-dimensional object is formed; (c) an optically transparent
member having a build surface, with said build surface and said
carrier defining a build region therebetween; (d) a liquid polymer
supply (e.g., a well) operatively associated with said build
surface and configured to supply liquid polymer into said build
region for solidification or polymerization; (e) a radiation source
configured to irradiate said build region through said optically
transparent member to form a solid polymer from said polymerizable
liquid; (f) optionally at least one drive operatively associated
with either said transparent member or said carrier; (g) a
controller operatively associated with said carrier, and/or
optionally said at least one drive, and said radiation source for
advancing said carrier away from said build surface to form said
three-dimensional object from said solid polymer, wherein said
optically transparent member comprises a build plate having an
optically transparent, gas-impermeable planar screen or base of
comprising: a lighting panel having individually addressable pixels
configured to selectively emit light and/or transmit light from
illumination below the pixels to a top surface top surface of the
lighting panel; a rigid, optically transparent, gas-impermeable
planar screen or base having an upper surface having an uneven
surface topology and a lower surface that is affixed to the top
surface of the lighting panel; a flexible, optically transparent,
gas-permeable sheet having upper and lower surfaces, the upper
surface comprising a build surface for forming a three-dimensional
object, the sheet lower surface positioned opposite the base,
wherein the build plate is configured to permit gas flow to the
build surface and the radiation source comprises the planar
screen.
58. The apparatus of claim 57, said controller further configured
to oscillate or reciprocate said carrier with respect to said build
surface to enhance or speed the refilling of said build region with
said polymerizable liquid.
59-63. (canceled)
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application Ser. No. 62/232,783 filed Sep. 25, 2015, the disclosure
of which is incorporated by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention concerns methods and apparatus for the
fabrication of solid three-dimensional objects from liquid
materials.
BACKGROUND OF THE INVENTION
[0003] In conventional additive or three-dimensional fabrication
techniques, construction of a three-dimensional object is performed
in a step-wise or layer-by-layer manner. In particular, layer
formation is performed through solidification of photo curable
resin under the action of visible or UV light irradiation. Two
techniques are known: one in which new layers are formed at the top
surface of the growing object; the other in which new layers are
formed at the bottom surface of the growing object.
[0004] If new layers are formed at the top surface of the growing
object, then after each irradiation step the object under
construction is lowered into the resin "pool," a new layer of resin
is coated on top, and a new irradiation step takes place. An early
example of such a technique is given in Hull, U.S. Pat. No.
5,236,637, at FIG. 3. A disadvantage of such "top down" techniques
is the need to submerge the growing object in a (potentially deep)
pool of liquid resin and reconstitute a precise overlayer of liquid
resin.
[0005] If new layers are formed at the bottom of the growing
object, then after each irradiation step the object under
construction must be separated from the bottom plate in the
fabrication well. An early example of such a technique is given in
Hull, U.S. Pat. No. 5,236,637, at FIG. 4. While such "bottom up"
techniques hold the potential to eliminate the need for a deep well
in which the object is submerged by instead lifting the object out
of a relatively shallow well or pool, a problem with such "bottom
up" fabrication techniques, as commercially implemented, is that
extreme care must be taken, and additional mechanical elements
employed, when separating the solidified layer from the bottom
plate due to physical and chemical interactions therebetween. For
example, in U.S. Pat. No. 7,438,846, an elastic separation layer is
used to achieve "non-destructive" separation of solidified material
at the bottom construction plane. Other approaches, such as the
B9Creator.TM. 3-dimensional printer marketed by B9Creations of
Deadwood, S.D., USA, employ a sliding build plate. See, e.g., M.
Joyce, US Patent App. 2013/0292862 and Y. Chen et al., US Patent
App. 2013/0295212 (both Nov. 7, 2013); see also Y. Pan et al., J
Manufacturing Sci. and Eng. 134, 051011-1 (Oct. 2012). Such
approaches introduce a mechanical step that may complicate the
apparatus, slow the method, and/or potentially distort the end
product.
[0006] Continuous processes for producing a three-dimensional
object are suggested at some length with respect to "top down"
techniques in U.S. Pat. No. 7,892,474, but this reference does not
explain how they may be implemented in "bottom up" systems in a
manner non-destructive to the article being produced. Accordingly,
there is a need for alternate methods and apparatus for
three-dimensional fabrication that can obviate the need for
mechanical separation steps in "bottom-up" fabrication.
SUMMARY OF THE INVENTION
[0007] Described herein are methods, systems and apparatus
(including associated control methods, systems and apparatus), for
the production of a three-dimensional object by additive
manufacturing. In preferred (but not necessarily limiting)
embodiments, the method is carried out continuously. In preferred
(but not necessarily limiting) embodiments, the three-dimensional
object is produced from a liquid interface. Hence they are
sometimes referred to, for convenience and not for purposes of
limitation, as "continuous liquid interphase printing" or
"continuous liquid interface production" ("CLIP") herein (the two
being used interchangeably). See, e.g., J. Tumbleston et al.,
Continuous liquid interface production of 3D objects, Science 347,
1349-1352 (published online Mar. 16, 2015). A schematic
representation of one embodiment thereof is given in FIG. 1 herein.
In some embodiments of the methods and compositions described above
and below, the polymerizable liquid has a viscosity of 500 or 1,000
centipoise or more at room temperature and/or under the operating
conditions of the method, up to a viscosity of 10,000, 20,000, or
50,000 centipoise or more, at room temperature and/or under the
operating conditions of the method.
[0008] In some embodiments, a build plate assembly for a
three-dimensional printer includes: a lighting panel having
individually addressable pixels configured to selectively emit
light and/or transmit light from illumination below the pixels to a
top surface top surface of the lighting panel; a rigid, optically
transparent, gas-impermeable planar screen or base having an upper
surface having an uneven surface topology and a lower surface that
is affixed to the top surface of the lighting panel; and a
flexible, optically transparent, gas-permeable sheet having upper
and lower surfaces, the upper surface comprising a build surface
for forming a three-dimensional object, the sheet lower surface
positioned opposite the base, wherein the build plate is configured
to permit gas flow to the build surface.
[0009] In some embodiments, the build plate assembly includes an
adhesive layer between the gas-permeable sheet and the base, and a
channel layer defining channels therein. The channel layer
comprises a permeable material such as a permeable polymer (e.g.,
poly(dimethylsiloxane) (PDMS). The channel layer defines channels
on a bottom surface opposite the adhesive. The channel layer is
adhered to the base by chemical bonding (e.g., oxidative
treatments, including oxygen plasma treatments, UV ozone treatments
and/or wet chemical treatments). The adhesive layer comprises a
gas-permeable adhesive. The adhesive layer comprises a
poly(dimethylsiloxane) (PDMS) film (e.g., a silicone transfer film
adhesive).
[0010] In some embodiments, the base comprises a top portion and a
bottom portion, wherein the top portion comprises a patterned rigid
polymer that provides the surface topology and the top portion is
adhered to the bottom portion. The top portion comprises a first
material and the bottom portion comprises a second material that is
different from the first material. The second material comprises
sapphire, glass and/or quartz.
[0011] In some embodiments, the build plate assembly comprises an
elastomeric layer between the channel layer and the base configured
to increase an elasticity of the build surface.
[0012] In some embodiments, the permeable sheet and/or channel
layer comprises a PDMS composite comprising fluorescent,
oxygen-sensing particles for sensing oxygen.
[0013] In some embodiments, the permeable sheet, elastomeric layer
and/or channel layer comprises a PDMS composite comprising
electrically conductive particles for heating a portion of the
build plate.
[0014] In some embodiments, the lighting panel comprises a LCD
panel. The lighting panel may be an OLED panel, an ultraviolet LED
light source array and/or a grey scale lighting panel.
[0015] In some embodiments, light guides in the build plate
correspond to the individually addressable pixels of the lighting
panel.
[0016] In some embodiments, the surface topology comprises random
or patterned features configured to maintain a predefined gap
between the planar base and portions of the gas-permeable
sheet.
[0017] In some embodiments, the gas-permeable sheet includes a
thickness, and the gap is less than or equal to five times the
thickness of the sheet.
[0018] In some embodiments, a region between the planar base and
the gas-permeable sheet comprises gap regions between the planar
base and the gas-permeable sheet in which a gap that is sufficient
to increase gas flow and reduce an area of wetting on the gas
permeable sheet is maintained. In some embodiments, the surface
topology comprises a rough surface having irregular and/or random
features. In some embodiments, the planar base is
oxygen-impermeable.
[0019] In some embodiments, the gas-permeable sheet is
oxygen-permeable. In some embodiments, the surface topology of the
planar base is formed by a mechanical abrasive, chemical, etching
and/or laser cutting. In some embodiments, the surface topology
comprises depressions or protrusions covering about 0.1% to about
20% of an area of the planar base. In some embodiments, the surface
topology comprises depressions or protrusions having a height or
depth of 0.1-5 .mu.m deep. In some embodiments, the surface
topology comprises depressions or protrusions having a diameter of
about 1 to about 10 .mu.m. In some embodiments, the surface
topology that increases gas flow to the build surface is on the
base upper surface. In some embodiments, the surface topology that
increases gas flow to the build surface is on the sheet lower
surface. In some embodiments, a thickness of the sheet is less than
about 150 .mu.m. In some embodiments, the base comprises sapphire,
glass, quartz or polymer. In some embodiments, the sheet comprises
a fluoropoloymer (e.g., a perfluoropolyether polymer). In some
embodiments, the surface topology has an optical scattering angle
of less than 20%, less than 15% or less than 10%.
[0020] In some embodiments, a method of forming a three-dimensional
object includes: providing a carrier and an optically transparent
member having a build surface, said carrier and said build surface
defining a build region therebetween; filling said build region
with a polymerizable liquid, continuously or intermittently
irradiating said build region with light through said optically
transparent member to form a solid polymer from said polymerizable
liquid, continuously or intermittently advancing (e.g.,
sequentially or concurrently with said irradiating step) said
carrier away from said build surface to form said three-dimensional
object from said solid polymer,-wherein said optically transparent
member comprises a build plate described herein.
[0021] In some embodiments, said filling, irradiating, and/or
advancing steps are carried out while also concurrently: (i)
continuously maintaining a dead zone of polymerizable liquid in
contact with said build surface, and (ii) continuously maintaining
a gradient of polymerization zone between said dead zone and said
solid polymer and in contact with each thereof, said gradient of
polymerization zone comprising said polymerizable liquid in
partially cured form.
[0022] In some embodiments, the carrier with said polymerized
region adhered thereto is unidirectionally advanced away from said
build surface on said stationary build plate.
[0023] In some embodiments, said filling step further comprising
vertically reciprocating said carrier with respect to said build
surface.sub.s to enhance or speed the refilling of said build
region with said polymerizable liquid.
[0024] In some embodiments, said vertically reciprocating step
comprises an upstroke and a downstroke, with the distance of said
upstroke greater than the distance of said downstroke, to thereby
concurrently carry out said advancing step in part or in whole.
[0025] In some embodiments, said vertically reciprocating step
comprises an upstroke, and wherein the speed of said upstroke
accelerates over a period of time during said upstroke.
[0026] In some embodiments, said upstroke begins gradually. In some
embodiments, said vertically reciprocating step comprises a
downstroke, and wherein the speed of said downstroke decelerates
over a period of time during said downstroke. In some embodiments,
said downstroke ends gradually.
[0027] In some embodiments, said vertically reciprocating step is
carried out over a total time of from 0.01 or 0.1 seconds up to 1
or 10 seconds, and/or over an upstroke distance of travel of from
0.02 or 0 2 millimeters to 1 or 10 millimeters.
[0028] In some embodiments, said advancing is carried out
intermittently at a rate of 1, 2, 5 or 10 individual advances per
minute up to 300, 600, or 1000 individual advances per minute, each
followed by a pause during which an irradiating step is carried
out.
[0029] In some embodiments, each of said individual advances is
carried out over an average distance of travel for each advance of
from 10 or 50 microns to 100 or 200 microns.
[0030] In some embodiments, said build surface is fixed and
stationary in the lateral (e.g., X and Y) dimensions.
[0031] In some embodiments, said build surface is fixed and
stationary in the vertical (or Z) dimension.
[0032] In some embodiments, said optically transparent member
comprises a semipermeable member, and said continuously maintaining
a dead zone is carried out by feeding an inhibitor of
polymerization through said optically transparent member in an
amount sufficient to maintain said dead zone and said gradient of
polymerization.
[0033] In some embodiments, said optically transparent member is
comprised of a semipermeable fluoropolymer, a rigid gas-permeable
polymer, porous glass, or a combination thereof.
[0034] In some embodiments, said gradient of polymerization zone
and said dead zone together have a thickness of from 1 to 1000
microns.
[0035] In some embodiments, said gradient of polymerization zone is
maintained for a time of at least 5, 10, 20, or 30 seconds, or at
least 1 or 2 minutes.
[0036] In some embodiments, the method includes the step of
disrupting said gradient of polymerization zone for a time
sufficient to form a cleavage line in said three-dimensional
object.
[0037] In some embodiments, the step of heating said polymerizable
liquid to reduce the viscosity thereof in said build region.
[0038] In some embodiments, said semipermeable member has a
thickness of from 0.1 to 100 millimeters; and/or wherein said
semipermeable member has a permeability to oxygen of at least
7.5.times.10.sup.-17 m.sup.2s.sup.-1Pa.sup.-1 (10 Barrers); and/or
wherein said semipermeable member is formed of a semipermeable
fluoropolymer, a rigid gas-permeable polymer, porous glass, or a
combination thereof
[0039] In some embodiments, said polymerizable liquid comprises a
free radical polymerizable liquid and said inhibitor comprises
oxygen; or said polymerizable liquid comprises an acid-catalyzed or
cationically polymerizable liquid, and said inhibitor comprises a
base.
[0040] In some embodiments, an apparatus for forming a
three-dimensional object from a polymerizable liquid includes: (a)
a support; (b) a carrier operatively associated with said support
on which carrier said three-dimensional object is formed; (c) an
optically transparent member having a build surface, with said
build surface and said carrier defining a build region
therebetween; (d) a liquid polymer supply (e.g., a well)
operatively associated with said build surface and configured to
supply liquid polymer into said build region for solidification or
polymerization; (e) a radiation source configured to irradiate said
build region through said optically transparent member to form a
solid polymer from said polymerizable liquid; (f) optionally at
least one drive operatively associated with either said transparent
member or said carrier; (g) a controller operatively associated
with said carrier, and/or optionally said at least one drive, and
said radiation source for advancing said carrier away from said
build surface to form said three-dimensional object from said solid
polymer, wherein said optically transparent member comprises a
build plate having an optically transparent, gas-impermeable planar
screen or base of any of claims 1 to 34, and the radiation source
comprises the planar screen.
[0041] In some embodiments, the controller is further configured to
oscillate or reciprocate said carrier with respect to said build
surface to enhance or speed the refilling of said build region with
said polymerizable liquid.
[0042] In some embodiments, the controller is further configured to
form said three-dimensional object from said solid polymer while
also concurrently with said filling, advancing, and/or irradiating
step: (i) continuously maintaining a dead zone of polymerizable
liquid in contact with said build surface, and (ii) continuously
maintaining a gradient of polymerization zone between said dead
zone and said solid polymer and in contact with each thereof, said
gradient of polymerization zone comprising said polymerizable
liquid in partially cured form
[0043] In some embodiments, the build plate is substantially fixed
or stationary.
[0044] In some embodiments, said semipermeable member comprises a
top surface portion, a bottom surface portion, and an edge surface
portion; said build surface is on said top surface portion; and
said feed surface is on at least one of said top surface portion,
said bottom surface portion, and said edge surface portion.
[0045] In some embodiments, said optically transparent member
comprises a semipermeable member. In some embodiments, said
semipermeable member has a thickness of from 0.1 to 100
millimeters; and/or wherein said semipermeable member has a
permeability to oxygen of at least 7.5.times.10.sup.-17
m.sup.2s.sup.-1Pa.sup.-1 (10 Barrers); and/or wherein said
semipermeable member is formed of a semipermeable fluoropolymer, a
rigid gas-permeable polymer, porous glass, or a combination
thereof.
[0046] Non-limiting examples and specific embodiments of the
present invention are explained in greater detail in the drawings
herein and the specification set forth below. The disclosure of all
United States Patent references cited herein are to be incorporated
herein by reference in their entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] FIG. 1 is a schematic illustration of one embodiment of a
method of the present invention.
[0048] FIG. 2 is a perspective view of one embodiment of an
apparatus of the present invention.
[0049] FIG. 3 is a first flow chart illustrating control systems
and methods for carrying out the present invention.
[0050] FIG. 4 is a second flow chart illustrating control systems
and methods for carrying out the present invention.
[0051] FIG. 5 is a third flow chart illustrating control systems
and methods for carrying out the present invention.
[0052] FIG. 6 is a graphic illustration of a process of the
invention indicating the position of the carrier in relation to the
build surface or plate, where both advancing of the carrier and
irradiation of the build region is carried out continuously.
Advancing of the carrier is illustrated on the vertical axis, and
time is illustrated on the horizontal axis.
[0053] FIG. 7 is a graphic illustration of another process of the
invention indicating the position of the carrier in relation to the
build surface or plate, where both advancing of the carrier and
irradiation of the build region is carried out stepwise, yet the
dead zone and gradient of polymerization are maintained. Advancing
of the carrier is again illustrated on the vertical axis, and time
is illustrated on the horizontal axis.
[0054] FIG. 8 is a graphic illustration of still another process of
the invention indicating the position of the carrier in relation to
the build surface or plate, where both advancing of the carrier and
irradiation of the build region is carried out stepwise, the dead
zone and gradient of polymerization are maintained, and a
reciprocating step is introduced between irradiation steps to
enhance the flow of polymerizable liquid into the build region.
Advancing of the carrier is again illustrated on the vertical axis,
and time is illustrated on the horizontal axis.
[0055] FIG. 9 is a detailed illustration of a reciprocation step of
FIG. 8, showing a period of acceleration occurring during the
upstroke (i.e., a gradual start of the upstroke) and a period of
deceleration occurring during the downstroke (i.e., a gradual end
to the downstroke).
[0056] FIG. 10 schematically illustrates the movement of the
carrier (z) over time (t) in the course of fabricating a
three-dimensional object by processes of the present invention
through a first base (or "adhesion") zone, a second transition
zone, and a third body zone.
[0057] FIG. 11A schematically illustrates the movement of the
carrier (z) over time (t) in the course of fabricating a
three-dimensional object by continuous advancing and continuous
exposure.
[0058] FIG. 11B illustrates the fabrication of a three-dimensional
object in a manner similar to FIG. 11A, except that illumination is
now in an intermittent (or "strobe") pattern.
[0059] FIG. 12A schematically illustrates the movement of the
carrier (z) over time (t) in the course of fabricating a
three-dimensional object by intermittent (or "stepped") advancing
and intermittent exposure.
[0060] FIG. 12B illustrates the fabrication of a three-dimensional
object in a manner similar to FIG. 12A, except that illumination is
now in a shortened intermittent (or "strobe") pattern.
[0061] FIG. 13A schematically illustrates the movement of the
carrier (z) over time (t) in the course of fabricating a
three-dimensional object by oscillatory advancing and intermittent
exposure.
[0062] FIG. 13B illustrates the fabrication of a three-dimensional
object in a manner similar to FIG. 13A, except that illumination is
now in a shortened intermittent (or "strobe") pattern.
[0063] FIG. 14A schematically illustrates one segment of a "strobe"
pattern of fabrication, where the duration of the static portion of
the carrier has been shortened to near the duration of the "strobe"
exposure
[0064] FIG. 14B is a schematic illustration of a segment of a
strobe pattern of fabrication similar to FIG. 14A, except that the
carrier is now moving slowly upward during the period of strobe
illumination.
[0065] FIG. 15A is a schematic illustration of the fabrication of a
three-dimensional object similar to FIG. 13A, except that the body
segment is fabricated in two contiguous segments, with the first
segment carried out in an oscillatory operating mode, and the
second segment carried out in a continuous operating mode.
[0066] FIG. 15B is a schematic illustration of the fabrication of a
three-dimensional object similar to FIG. 15A, except that
oscillatory operating modes are replaced with stepped operating
modes.
[0067] FIG. 16A is a schematic illustration of the fabrication of a
three-dimensional object similar to FIG. 11A, except that the body
segment is fabricated in three contiguous segments, with the first
and third segments carried out in a continuous operating mode, and
the second segment carried out in oscillatory operating mode.
[0068] FIG. 16B is a schematic illustration of the fabrication of a
three-dimensional object similar to FIG. 16A, except that the
oscillatory operating mode is replaced with a stepped operating
mode.
[0069] FIG. 17A is a schematic illustration of the fabrication of a
three-dimensional object similar to FIG. 16A, except that the base
zone, transition zone, and first segment of the body zone are
carried out in a strobe continuous operating mode, the second
segment of the body zone is fabricated in an oscillatory operating
mode, and the third segment of the body zone is fabricated in a
continuous operating mode.
[0070] FIG. 17B is similar to FIG. 17A, except that the second
segment of the body zone is fabricated in a stepped operating
mode.
[0071] FIG. 18A is a schematic illustration of the fabrication of a
three-dimensional object similar to FIG. 11A, except that light
intensity is varied in the course of fabricating the base and
transition zones, and both light intensity and rate of advancing
are varied in the course of fabricating the body zone.
[0072] FIG. 18B is a schematic illustration of the fabrication of a
three-dimensional object similar to FIG. 17A, except that light is
interrupted in an intermittent fashion (dashed line representing
light intensity during interrupted segments is for comparison to
FIG. 17A only).
[0073] FIG. 19 is a schematic illustration of the fabrication of a
three-dimensional object similar to FIG. 11A, except that the mode
of operation during fabrication of the body segment is changed
multiple times for continuous, to reciprocal, and back.
[0074] FIG. 20 schematically illustrates parameters that may be
varied within a reciprocal or step-wise operating mode.
[0075] FIG. 21A schematically illustrates a method of the invention
carried out in a continuous operating mode, with constant slice
thickness and constant carrier speed.
[0076] FIG. 21B schematically illustrates a method of the invention
carried out in a continuous operating mode, with variable slice
thickness with constant carrier speed.
[0077] FIG. 21C schematically illustrates a method of the invention
carried out in a continuous operating mode, with constant slice
thickness and variable carrier speed.
[0078] FIG. 21D schematically illustrates a method of the invention
carried out in continuous operating mode, mode with variable slice
thickness and variable carrier speed.
[0079] FIG. 21E schematically illustrates a method of the invention
carried out in reciprocal operating mode, with constant slice
thickness.
[0080] FIG. 21F schematically illustrates a method of the invention
carried out in reciprocal operating mode, with variable slice
thickness.
[0081] FIG. 22 is a side cross sectional view of a build plate with
a permeable sheet having channels therein according to some
embodiments.
[0082] FIG. 23 is a side cross sectional view of a build plate with
a patterned base layer and a lighting panel according to some
embodiments.
[0083] FIG. 24 is a side cross sectional view of a build plate with
channel layers and a lighting panel according to some
embodiments.
[0084] FIG. 25 is a side cross sectional view of a build plate with
channel layers and a lighting panel according to some
embodiments.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0085] The present invention is now described more fully
hereinafter with reference to the accompanying drawings, in which
embodiments of the invention are shown. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather
these embodiments are provided so that this disclosure will be
thorough and complete and will fully convey the scope of the
invention to those skilled in the art.
[0086] Like numbers refer to like elements throughout. In the
figures, the thickness of certain lines, layers, components,
elements or features may be exaggerated for clarity. Where used,
broken lines illustrate optional features or operations unless
specified otherwise.
[0087] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a," "an" and
"the" are intended to include plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements components and/or groups or
combinations thereof, but do not preclude the presence or addition
of one or more other features, integers, steps, operations,
elements, components and/or groups or combinations thereof.
[0088] As used herein, the term "and/or" includes any and all
possible combinations or one or more of the associated listed
items, as well as the lack of combinations when interpreted in the
alternative ("or").
[0089] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the specification and claims and should
not be interpreted in an idealized or overly formal sense unless
expressly so defined herein. Well-known functions or constructions
may not be described in detail for brevity and/or clarity.
[0090] It will be understood that when an element is referred to as
being "on," "attached" to, "connected" to, "coupled" with,
"contacting," etc., another element, it can be directly on,
attached to, connected to, coupled with and/or contacting the other
element or intervening elements can also be present. In contrast,
when an element is referred to as being, for example, "directly
on," "directly attached" to, "directly connected" to, "directly
coupled" with or "directly contacting" another element, there are
no intervening elements present. It will also be appreciated by
those of skill in the art that references to a structure or feature
that is disposed "adjacent" another feature can have portions that
overlap or underlie the adjacent feature.
[0091] Spatially relative terms, such as "under," "below," "lower,"
"over," "upper" and the like, may be used herein for ease of
description to describe an element's or feature's relationship to
another element(s) or feature(s) as illustrated in the figures. It
will be understood that the spatially relative terms are intended
to encompass different orientations of the device in use or
operation in addition to the orientation depicted in the figures.
For example, if the device in the figures is inverted, elements
described as "under" or "beneath" other elements or features would
then be oriented "over" the other elements or features. Thus the
exemplary term "under" can encompass both an orientation of over
and under. The device may otherwise be oriented (rotated 90 degrees
or at other orientations) and the spatially relative descriptors
used herein interpreted accordingly. Similarly, the terms
"upwardly," "downwardly," "vertical," "horizontal" and the like are
used herein for the purpose of explanation only, unless
specifically indicated otherwise.
[0092] It will be understood that, although the terms first,
second, etc., may be used herein to describe various elements,
components, regions, layers and/or sections, these elements,
components, regions, layers and/or sections should not be limited
by these terms. Rather, these terms are only used to distinguish
one element, component, region, layer and/or section, from another
element, component, region, layer and/or section. Thus, a first
element, component, region, layer or section discussed herein could
be termed a second element, component, region, layer or section
without departing from the teachings of the present invention. The
sequence of operations (or steps) is not limited to the order
presented in the claims or figures unless specifically indicated
otherwise.
1. Polymerizable Liquids/Part A Components.
[0093] Any suitable polymerizable liquid can be used to enable the
present invention. The liquid (sometimes also referred to as
"liquid resin" "ink," or simply "resin" herein) can include a
monomer, particularly photopolymerizable and/or free radical
polymerizable monomers, and a suitable initiator such as a free
radical initiator, and combinations thereof. Examples include, but
are not limited to, acrylics, methacrylics, acrylamides, styrenics,
olefins, halogenated olefms, cyclic alkenes, maleic anhydride,
alkenes, alkynes, carbon monoxide, functionalized oligomers,
multifunctional cure site monomers, functionalized PEGs, etc.,
including combinations thereof Examples of liquid resins, monomers
and initiators include but are not limited to those set forth in
U.S. Pat. Nos. 8,232,043; 8,119,214; 7,935,476; 7,767,728;
7,649,029; WO 2012129968 Al; CN 102715751 A; JP 2012210408 A.
[0094] Acid catalyzed polymerizable liquids. While in some
embodiments as noted above the polymerizable liquid comprises a
free radical polymerizable liquid (in which case an inhibitor may
be oxygen as described below), in other embodiments the
polymerizable liquid comprises an acid catalyzed, or cationically
polymerized, polymerizable liquid. In such embodiments the
polymerizable liquid comprises monomers contain groups suitable for
acid catalysis, such as epoxide groups, vinyl ether groups, etc.
Thus suitable monomers include olefins such as methoxyethene,
4-methoxystyrene, styrene, 2-methylprop-1-ene, 1,3-butadiene, etc.;
heterocycloic monomers (including lactones, lactams, and cyclic
amines) such as oxirane, thietane, tetrahydrofuran, oxazoline, 1,3,
dioxepane, oxetan-2-one, etc., and combinations thereof A suitable
(generally ionic or non-ionic) photoacid generator (PAG) is
included in the acid catalyzed polymerizable liquid, examples of
which include, but are not limited to onium salts, sulfonium and
iodonium salts, etc., such as diphenyl iodide hexafluorophosphate,
diphenyl iodide hexafluoroarsenate, diphenyl iodide
hexafluoroantimonate, diphenyl p-methoxyphenyl triflate, diphenyl
p-toluenyl triflate, diphenyl p-isobutylphenyl triflate, diphenyl
p-tert-butylphenyl triflate, triphenylsulfonium
hexafluororphosphate, triphenylsulfonium hexafluoroarsenate,
triphenylsulfonium hexafluoroantimonate, triphenylsulfonium
triflate, dibutylnaphthylsulfonium triflate, etc., including
mixtures thereof. See, e.g., U.S. Pat. Nos. 7,824,839; 7,550,246;
7,534,844; 6,692,891; 5,374,500; and 5,017,461; see also Photoacid
Generator Selection Guide for the electronics industry and energy
curable coatings (BASF 2010).
[0095] Hydrogels. In some embodiments suitable resins includes
photocurable hydrogels like poly(ethylene glycols) (PEG) and
gelatins. PEG hydrogels have been used to deliver a variety of
biologicals, including Growth factors; however, a great challenge
facing PEG hydrogels crosslinked by chain growth polymerizations is
the potential for irreversible protein damage. Conditions to
maximize release of the biologicals from photopolymerized PEG
diacrylate hydrogels can be enhanced by inclusion of affinity
binding peptide sequences in the monomer resin solutions, prior to
photopolymerization allowing sustained delivery. Gelatin is a
biopolymer frequently used in food, cosmetic, pharmaceutical and
photographic industries.
[0096] It is obtained by thermal denaturation or chemical and
physical degradation of collagen. There are three kinds of gelatin,
including those found in animals, fish and humans. Gelatin from the
skin of cold water fish is considered safe to use in pharmaceutical
applications. UV or visible light can be used to crosslink
appropriately modified gelatin. Methods for crosslinking gelatin
include cure derivatives from dyes such as Rose Bengal.
[0097] Photocurable silicone resins. A suitable resin includes
photocurable silicones. UV cure silicone rubber, such as
Siopren.TM. UV Cure Silicone Rubber can be used as can LOCTITE.TM.
Cure Silicone adhesives sealants. Applications include optical
instruments, medical and surgical equipment, exterior lighting and
enclosures, electrical connectors/sensors, fiber optics and
gaskets.
[0098] Biodegradable resins. Biodegradable resins are particularly
important for implantable devices to deliver drugs or for temporary
performance applications, like biodegradable screws and stents
(U.S. Pat. Nos. 7,919,162; 6,932,930). Biodegradable copolymers of
lactic acid and glycolic acid (PLGA) can be dissolved in PEG
dimethacrylate to yield a transparent resin suitable for use.
Polycaprolactone and PLGA oligomers can be functionalized with
acrylic or methacrylic groups to allow them to be effective resins
for use.
[0099] Photocurable polyurethanes. A particularly useful resin is
photocurable polyurethanes. A photopolymerizable polyurethane
composition comprising (1) a polyurethane based on an aliphatic
diisocyanate, poly(hexamethylene isophthalate glycol) and,
optionally, 1,4-butanediol; (2) a polyfunctional acrylic ester; (3)
a photoinitiator; and (4) an anti-oxidant, can be formulated so
that it provides a hard, abrasion-resistant, and stain-resistant
material (U.S. Pat. No. 4,337,130). Photocurable thermoplastic
polyurethane elastomers incorporate photoreactive diacetylene diols
as chain extenders.
[0100] High performance resins. In some embodiments, high
performance resins are used. Such high performance resins may
sometimes require the use of heating to melt and/or reduce the
viscosity thereof, as noted above and discussed further below.
Examples of such resins include, but are not limited to, resins for
those materials sometimes referred to as liquid crystalline
polymers of esters, ester-imide, and ester-amide oligomers, as
described in U.S. Pat. Nos. 7,507,784; 6,939,940. Since such resins
are sometimes employed as high-temperature thermoset resins, in the
present invention they further comprise a suitable photoinitiator
such as benzophenone, anthraquinone, and fluoroenone initiators
(including derivatives thereof), to initiate cross-linking on
irradiation, as discussed further below.
[0101] Additional example resins. Particularly useful resins for
dental applications include EnvisionTEC's Clear Guide,
EnvisionTEC's E-Denstone Material. Particularly useful resins for
hearing aid industries include EnvisionTEC's e-Shell 300 Series of
resins. Particularly useful resins include EnvisionTEC's HTM140IV
High Temperature Mold Material for use directly with vulcanized
rubber in molding/casting applications. A particularly useful
material for making tough and stiff parts includes EnvisionTEC's
RC31 resin. A particularly useful resin for investment casting
applications includes EnvisionTEC's Easy Cast EC500.
[0102] Additional resin ingredients. The liquid resin or
polymerizable material can have solid particles suspended or
dispersed therein. Any suitable solid particle can be used,
depending upon the end product being fabricated. The particles can
be metallic, organic/polymeric, inorganic, or composites or
mixtures thereof. The particles can be nonconductive,
semi-conductive, or conductive (including metallic and non-metallic
or polymer conductors); and the particles can be magnetic,
ferromagnetic, paramagnetic, or nonmagnetic. The particles can be
of any suitable shape, including spherical, elliptical,
cylindrical, etc. The particles can comprise an active agent or
detectable compound as described below, though these may also be
provided dissolved solubilized in the liquid resin as also
discussed below. For example, magnetic or paramagnetic particles or
nanoparticles can be employed. The resin or polymerizable material
may contain a dispersing agent, such as an ionic surfactant, a
non-ionic surfactant, a block copolymer, or the like.
[0103] The liquid resin can have additional ingredients solubilized
therein, including pigments, dyes, active compounds or
pharmaceutical compounds, detectable compounds (e.g., fluorescent,
phosphorescent, radioactive), etc., again depending upon the
particular purpose of the product being fabricated. Examples of
such additional ingredients include, but are not limited to,
proteins, peptides, nucleic acids (DNA, RNA) such as siRNA, sugars,
small organic compounds (drugs and drug-like compounds), etc.,
including combinations thereof.
[0104] Inhibitors of polymerization. Inhibitors or polymerization
inhibitors for use in the present invention may be in the form of a
liquid or a gas. In some embodiments, gas inhibitors are preferred.
The specific inhibitor will depend upon the monomer being
polymerized and the polymerization reaction. For free radical
polymerization monomers, the inhibitor can conveniently be oxygen,
which can be provided in the form of a gas such as air, a gas
enriched in oxygen (optionally but in some embodiments preferably
containing additional inert gases to reduce combustibility
thereof), or in some embodiments pure oxygen gas. In alternate
embodiments, such as where the monomer is polymerized by photoacid
generator initiator, the inhibitor can be a base such as ammonia,
trace amines (e.g. methyl amine, ethyl amine, di and trialkyl
amines such as dimethyl amine, diethyl amine, trimethyl amine,
triethyl amine, etc.), or carbon dioxide, including mixtures or
combinations thereof
[0105] Polymerizable liquids carrying live cells. In some
embodiments, the polymerizable liquid may carry live cells as
"particles" therein. Such polymerizable liquids are generally
aqueous, and may be oxygenated, and may be considered as
"emulsions" where the live cells are the discrete phase. Suitable
live cells may be plant cells (e.g., monocot, dicot), animal cells
(e.g., mammalian, avian, amphibian, reptile cells), microbial cells
(e.g., prokaryote, eukaryote, protozoal, etc.), etc. The cells may
be of differentiated cells from or corresponding to any type of
tissue (e.g., blood, cartilage, bone, muscle, endocrine gland,
exocrine gland, epithelial, endothelial, etc.), or may be
undifferentiated cells such as stem cells or progenitor cells. In
such embodiments the polymerizable liquid can be one that forms a
hydrogel, including but not limited to those described in U.S. Pat.
Nos. 7,651,683; 7,651,682; 7,556,490; 6,602,975; 5,836,313;
etc.
2. Apparatus.
[0106] A non-limiting embodiment of an apparatus of the invention
is shown in FIG. 2. It comprises a radiation source 11 such as a
digital light processor (DLP) providing electromagnetic radiation
12 which though reflective mirror 13 illuminates a build chamber
defined by wall 14 and a rigid build plate 15 forming the bottom of
the build chamber, which build chamber is filled with liquid resin
16. The bottom of the chamber 15 is constructed of build plate
comprising a semipermeable member as discussed further below. The
top of the object under construction 17 is attached to a carrier
18. The carrier is driven in the vertical direction by linear stage
19, although alternate structures can be used as discussed
below.
[0107] A liquid resin reservoir, tubing, pumps liquid level sensors
and/or valves can be included to replenish the pool of liquid resin
in the build chamber (not shown for clarity) though in some
embodiments a simple gravity feed may be employed. Drives/actuators
for the carrier or linear stage, along with associated wiring, can
be included in accordance with known techniques (again not shown
for clarity). The drives/actuators, radiation source, and in some
embodiments pumps and liquid level sensors can all be operatively
associated with a suitable controller, again in accordance with
known techniques.
[0108] Build plates 15 used to carry out the present invention
generally comprise or consist of a (typically rigid or solid,
stationary, and/or fixed) semipermeable (or gas permeable) member,
alone or in combination with one or more additional supporting
substrates (e.g., clamps and tensioning members to rigidify an
otherwise flexible semipermeable material). The semipermeable
member can be made of any suitable material that is optically
transparent at the relevant wavelengths (or otherwise transparent
to the radiation source, whether or not it is visually transparent
as perceived by the human eye--i.e., an optically transparent
window may in some embodiments be visually opaque), including but
not limited to porous or microporous glass, and the rigid gas
permeable polymers used for the manufacture of rigid gas permeable
contact lenses. See, e.g., Norman G. Gaylord, U.S. Pat. No.
RE31,406; see also U.S. Pat. Nos. 7,862,176; 7,344,731; 7,097,302;
5,349,394; 5,310,571; 5,162,469; 5,141,665; 5,070,170; 4,923,906;
and 4,845,089. In some embodiments such materials are characterized
as glassy and/or amorphous polymers and/or substantially
crosslinked that they are essentially non-swellable. Preferably the
semipermeable member is formed of a material that does not swell
when contacted to the liquid resin or material to be polymerized
(i.e., is "non-swellable"). Suitable materials for the
semipermeable member include amorphous fluoropolymers, such as
those described in U.S. Pat. Nos. 5,308,685 and 5,051,115. For
example, such fluoropolymers are particularly useful over silicones
that would potentially swell when used in conjunction with organic
liquid resin inks to be polymerized. For some liquid resin inks,
such as more aqueous-based monomeric systems and/or some polymeric
resin ink systems that have low swelling tendencies, silicone based
window materials maybe suitable. The solubility or permeability of
organic liquid resin inks can be dramatically decreased by a number
of known parameters including increasing the crosslink density of
the window material or increasing the molecular weight of the
liquid resin ink. In some embodiments the build plate may be formed
from a thin film or sheet of material which is flexible when
separated from the apparatus of the invention, but which is clamped
and tensioned when installed in the apparatus (e.g., with a
tensioning ring) so that it is rendered fixed or rigid in the
apparatus. Particular materials include TEFLON AF.RTM.
fluoropolymers, commercially available from DuPont. Additional
materials include perfluoropolyether polymers such as described in
U.S. Pat. Nos. 8,268,446; 8,263,129; 8,158,728; and 7,435,495.
[0109] It will be appreciated that essentially all solid materials,
and most of those described above, have some inherent "flex" even
though they may be considered "rigid," depending on factors such as
the shape and thickness thereof and environmental factors such as
the pressure and temperature to which they are subjected. In
addition, the terms "stationary" or "fixed" with respect to the
build plate is intended to mean that no mechanical interruption of
the process occurs, or no mechanism or structure for mechanical
interruption of the process (as in a layer-by-layer method or
apparatus) is provided, even if a mechanism for incremental
adjustment of the build plate (for example, adjustment that does
not lead to or cause collapse of the gradient of polymerization
zone) is provided), or if the build surface contributes to
reciprocation to aid feeding of the polymerizable liquid, as
described further below.
[0110] The semipermeable member typically comprises a top surface
portion, a bottom surface portion, and an edge surface portion. The
build surface is on the top surface portion; and the feed surface
may be on one, two, or all three of the top surface portion, the
bottom surface portion, and/or the edge surface portion. In the
embodiment illustrated in FIG. 2 the feed surface is on the bottom
surface portion, but alternate configurations where the feed
surface is provided on an edge, and/or on the top surface portion
(close to but separate or spaced away from the build surface) can
be implemented with routine skill.
[0111] The semipermeable member has, in some embodiments, a
thickness of from 0.01, 0.1 or 1 millimeters to 10 or 100
millimeters, or more (depending upon the size of the item being
fabricated, whether or not it is laminated to or in contact with an
additional supporting plate such as glass, etc., as discussed
further below.
[0112] The permeability of the semipermeable member to the
polymerization inhibitor will depend upon conditions such as the
pressure of the atmosphere and/or inhibitor, the choice of
inhibitor, the rate or speed of fabrication, etc. In general, when
the inhibitor is oxygen, the permeability of the semipermeable
member to oxygen may be from 10 or 20 Barrers, up to 1000 or 2000
Barrers, or more. For example, a semipermeable member with a
permeability of 10 Barrers used with a pure oxygen, or highly
enriched oxygen, atmosphere under a pressure of 150 PSI may perform
substantially the same as a semipermeable member with a
permeability of 500 Barrers when the oxygen is supplied from the
ambient atmosphere under atmospheric conditions.
[0113] Thus, the semipermeable member may comprise a flexible
polymer film (having any suitable thickness, e.g., from 0.001,
0.01, 0.05, 0.1 or 1 millimeters to 1, 5, 10, or 100 millimeters,
or more), and the build plate may further comprise a tensioning
member (e.g., a peripheral clamp and an operatively associated
strain member or stretching member, as in a "drum head"; a
plurality of peripheral clamps, etc., including combinations
thereof) connected to the polymer film and to fix and rigidify the
film (e.g., at least sufficiently so that the film does not stick
to the object as the object is advanced and resiliently or
elastically rebound therefrom). The film has a top surface and a
bottom surface, with the build surface on the top surface and the
feed surface preferably on the bottom surface. In other
embodiments, the semipermeable member comprises: (i) a polymer film
layer (having any suitable thickness, e.g., from 0.001, 0.01, 0.1
or 1 millimeters to 5, 10 or 100 millimeters, or more), having a
top surface positioned for contacting said polymerizable liquid and
a bottom surface, and (ii) a rigid, gas permeable, optically
transparent supporting member (having any suitable thickness, e.g.,
from 0.01, 0.1 or 1 millimeters to 10, 100, or 200 millimeters, or
more), contacting said film layer bottom surface. The supporting
member has a top surface contacting the film layer bottom surface,
and the supporting member has a bottom surface which may serve as
the feed surface for the polymerization inhibitor. Any suitable
materials that are semipermeable (that is, permeable to the
polymerization inhibitor) may be used. For example, the polymer
film or polymer film layer may, for example, be a fluoropolymer
film, such as an amorphous thermoplastic fluoropolymer like TEFLON
AF 1600.TM. or TEFLON AF 2400.TM. fluoropolymer films, or
perfluoropolyether (PFPE), particularly a crosslinked PFPE film, or
a crosslinked silicone polymer film. The supporting member
comprises a silicone or crosslinked silicone polymer member such as
a polydmiethylxiloxane member, a rigid gas permeable polymer
member, or a porous or microporous glass member. Films can be
laminated or clamped directly to the rigid supporting member
without adhesive (e.g., using PFPE and PDMS materials), or silane
coupling agents that react with the upper surface of a PDMS layer
can be utilized to adhere to the first polymer film layer.
UV-curable, acrylate-functional silicones can also be used as a tie
layer between UV-curable PFPEs and rigid PDMS supporting
layers.
[0114] When configured for placement in the apparatus, the carrier
defines a "build region" on the build surface; within the total
area of the build surface. Because lateral "throw" (e.g., in the X
and/or Y directions) is not required in the present invention to
break adhesion between successive layers, as in the Joyce and Chen
devices noted previously, the area of the build region within the
build surface may be maximized (or conversely, the area of the
build surface not devoted to the build region may be minimized).
Hence in some embodiments, the total surface area of the build
region can occupy at least fifty, sixty, seventy, eighty, or ninety
percent of the total surface area of the build surface.
[0115] As shown in FIG. 2, the various components are mounted on a
support or frame assembly 20. While the particular design of the
support or frame assembly is not critical and can assume numerous
configurations, in the illustrated embodiment it is comprised of a
base 21 to which the radiation source 11 is securely or rigidly
attached, a vertical member 22 to which the linear stage is
operatively associated, and a horizontal table 23 to which wall 14
is removably or securely attached (or on which the wall is placed),
and with the build plate rigidly fixed, either permanently or
removably, to form the build chamber as described above.
[0116] As noted above, the build plate can consist of a single
unitary and integral piece of a rigid semipermeable member, or can
comprise additional materials. For example, a porous or microporous
glass can be laminated or fixed to a rigid semipermeable material.
Or, a semipermeable member as an upper portion can be fixed to a
transparent lower member having purging channels formed therein for
feeding gas carrying the polymerization inhibitor to the
semipermeable member (through which it passes to the build surface
to facilitate the formation of a release layer of unpolymerized
liquid material, as noted above and below). Such purge channels may
extend fully or partially through the base plate: For example, the
purge channels may extend partially into the base plate, but then
end in the region directly underlying the build surface to avoid
introduction of distortion. Specific geometries will depend upon
whether the feed surface for the inhibitor into the semipermeable
member is located on the same side or opposite side as the build
surface, on an edge portion thereof, or a combination of several
thereof.
[0117] Any suitable radiation source (or combination of sources)
can be used, depending upon the particular resin employed,
including electron beam and ionizing radiation sources. In a
preferred embodiment the radiation source is an actinic radiation
source, such as one or more light sources, and in particular one or
more ultraviolet light sources. Any suitable light source can be
used, such as incandescent lights, fluorescent lights,
phosphorescent or luminescent lights, a laser, light-emitting
diode, etc., including arrays thereof. The light source preferably
includes a pattern-forming element operatively associated with a
controller, as noted above. In some embodiments, the light source
or pattern forming element comprises a digital (or deformable)
micromirror device (DMD) with digital light processing (DLP), a
spatial modulator (SLM), or a microelectromechanical system (MEMS)
mirror array, a mask (aka a reticle), a silhouette, or a
combination thereof See, U.S. Pat. No. 7,902,526. Preferably the
light source comprises a spatial light modulation array such as a
liquid crystal light valve array or micromirror array or DMD (e.g.,
with an operatively associated digital light processor, typically
in turn under the control of a suitable controller), configured to
carry out exposure or irradiation of the polymerizable liquid
without a mask, e.g., by maskless photolithography. See, e.g., U.S.
Pat. Nos. 6,312,134; 6,248,509; 6,238,852; and 5,691,541.
[0118] In some embodiments, as discussed further below, there may
be movement in the X and/or Y directions concurrently with movement
in the Z direction, with the movement in the X and/or Y direction
hence occurring during polymerization of the polymerizable liquid
(this is in contrast to the movement described in Y. Chen et al.,
or M. Joyce, supra, which is movement between prior and subsequent
polymerization steps for the purpose of replenishing polymerizable
liquid). In the present invention such movement may be carried out
for purposes such as reducing "burn in" or fouling in a particular
zone of the build surface.
[0119] Because an advantage of some embodiments of the present
invention is that the size of the build surface on the
semipermeable member (i.e., the build plate or window) may be
reduced due to the absence of a requirement for extensive lateral
"throw" as in the Joyce or Chen devices noted above, in the
methods, systems and apparatus of the present invention lateral
movement (including movement in the X and/or Y direction or
combination thereof) of the carrier and object (if such lateral
movement is present) is preferably not more than, or less than, 80,
70, 60, 50, 40, 30, 20, or even 10 percent of the width (in the
direction of that lateral movement) of the build region.
[0120] While in some embodiments the carrier is mounted on an
elevator to advance up and away from a stationary build plate, on
other embodiments the converse arrangement may be used: That is,
the carrier may be fixed and the build plate lowered to thereby
advance the carrier away therefrom. Numerous different mechanical
configurations will be apparent to those skilled in the art to
achieve the same result.
[0121] Depending on the choice of material from which the carrier
is fabricated, and the choice of polymer or resin from which the
article is made, adhesion of the article to the carrier may
sometimes be insufficient to retain the article on the carrier
through to completion of the finished article or "build." For
example, an aluminum carrier may have lower adhesion than a
poly(vinyl chloride) (or "PVC") carrier. Hence one solution is to
employ a carrier comprising a PVC on the surface to which the
article being fabricated is polymerized. If this promotes too great
an adhesion to conveniently separate the finished part from the
carrier, then any of a variety of techniques can be used to further
secure the article to a less adhesive carrier, including but not
limited to the application of adhesive tape such as "Greener
Masking Tape for Basic Painting #2025 High adhesion" to further
secure the article to the carrier during fabrication.
3. Controller and Process Control.
[0122] The methods and apparatus of the invention can include
process steps and apparatus features to implement process control,
including feedback and feed-forward control, to, for example,
enhance the speed and/or reliability of the method.
[0123] A controller for use in carrying out the present invention
may be implemented as hardware circuitry, software, or a
combination thereof. In one embodiment, the controller is a general
purpose computer that runs software, operatively associated with
monitors, drives, pumps, and other components through suitable
interface hardware and/or software. Suitable software for the
control of a three-dimensional printing or fabrication method and
apparatus as described herein includes, but is not limited to, the
ReplicatorG open source 3d printing program, 3DPrint.TM. controller
software from 3D systems, Slic3r, Skeinforge, KISSlicer,
Repetier-Host, PrintRun, Cura, etc., including combinations
thereof.
[0124] Process parameters to directly or indirectly monitor,
continuously or intermittently, during the process(e.g., during
one, some or all of said filling, irradiating and advancing steps)
include, but are not limited to, irradiation intensity, temperature
of carrier, polymerizable liquid in the build zone, temperature of
growing product, temperature of build plate, pressure, speed of
advance, pressure, force (e.g., exerted on the build plate through
the carrier and product being fabricated), strain (e.g., exerted on
the carrier by the growing product being fabricated), thickness of
release layer, etc.
[0125] Known parameters that may be used in feedback and/or
feed-forward control systems include, but are not limited to,
expected consumption of polymerizable liquid (e.g., from the known
geometry or volume of the article being fabricated), degradation
temperature of the polymer being formed from the polymerizable
liquid, etc.
[0126] Process conditions to directly or indirectly control,
continuously or step-wise, in response to a monitored parameter,
and/or known parameters (e.g., during any or all of the process
steps noted above), include, but are not limited to, rate of supply
of polymerizable liquid, temperature, pressure, rate or speed of
advance of carrier, intensity of irradiation, duration of
irradiation (e.g. for each "slice"), etc.
[0127] For example, the temperature of the polymerizable liquid in
the build zone, or the temperature of the build plate, can be
monitored, directly or indirectly with an appropriate thermocouple,
non-contact temperature sensor (e.g., an infrared temperature
sensor), or other suitable temperature sensor, to determine whether
the temperature exceeds the degradation temperature of the
polymerized product. If so, a process parameter may be adjusted
through a controller to reduce the temperature in the build zone
and/or of the build plate. Suitable process parameters for such
adjustment may include: decreasing temperature with a cooler,
decreasing the rate of advance of the carrier, decreasing intensity
of the irradiation, decreasing duration of radiation exposure,
etc.
[0128] In addition, the intensity of the irradiation source (e.g.,
an ultraviolet light source such as a mercury lamp) may be
monitored with a photodetector to detect a decrease of intensity
from the irriadiation source (e.g., through routine degredation
thereof during use). If detected, a process parameter may be
adjusted through a controller to accommodate the loss of intensity.
Suitable process parameters for such adjustment may include:
increasing temperature with a heater, decreasing the rate of
advance of the carrier, increasing power to the light source,
etc.
[0129] As another example, control of temperature and/or pressure
to enhance fabrication time may be achieved with heaters and
coolers (individually, or in combination with one another and
separately responsive to a controller), and/or with a pressure
supply (e.g., pump, pressure vessel, valves and combinations
thereof) and/or a pressure release mechanism such as a controllable
valve (individually, or in combination with one another and
separately responsive to a controller). Examples of heaters and
coolers include fluid circulation conduits, heaters/coolers
positioned adjacent elements of the apparatus or embedded into the
apparatus, thermoelectric devices, and the like.
[0130] In some embodiments the controller is configured to maintain
the gradient of polymerization zone described herein (see, e.g.,
FIG. 1) throughout the fabrication of some or all of the final
product. The specific configuration (e.g., times, rate or speed of
advancing, radiation intensity, temperature, etc.) will depend upon
factors such as the nature of the specific polymerizable liquid and
the product being created. Configuration to maintain the gradient
of polymerization zone may be carried out empirically, by entering
a set of process parameters or instructions previously determined,
or determined through a series of test runs or "trial and error";
the configuration may be provided through pre-determined
instructions; the configuration may be achieved by suitable
monitoring and feedback (as discussed above), combinations thereof,
or in any other suitable manner.
[0131] In some embodiments, a method and apparatus as described
above may be controlled by a software program running in a general
purpose computer with suitable interface hardware between that
computer and the apparatus described above. Numerous alternatives
are commercially available. Non-limiting examples of one
combination of components is shown in FIGS. 3 to 5, where
"Microcontroller" is Parallax Propeller, the Stepper Motor Driver
is Sparkfun EasyDriver, the LED Driver is a Luxeon Single LED
Driver, the USB to Serial is a Parallax USB to Serial converter,
and the DLP System is a Texas Instruments LightCrafter system.
4. General Methods.
[0132] As noted above, the present invention provides a method of
forming a three-dimensional object, comprising the steps of: (a)
providing a carrier and a build plate, said build plate comprising
a semipermeable member, said semipermeable member comprising a
build surface and a feed surface separate from said build surface,
with said build surface and said carrier defining a build region
therebetween, and with said feed surface in fluid contact with a
polymerization inhibitor; then (concurrently and/or sequentially)
(b) filing said build region with a polymerizable liquid, said
polymerizable liquid contacting said build segment, (c) irradiating
said build region through said build plate to produce a solid
polymerized region in said build region, with a liquid film release
layer comprised of said polymerizable liquid formed between said
solid polymerized region and said build surface, the polymerization
of which liquid film is inhibited by said polymerization inhibitor;
and (d) advancing said carrier with said polymerized region adhered
thereto away from said build surface on said stationary build plate
to create a subsequent build region between said polymerized region
and said top zone. In general the method includes (e) continuing
and/or repeating steps (b) through (d) to produce a subsequent
polymerized region adhered to a previous polymerized region until
the continued or repeated deposition of polymerized regions adhered
to one another forms said three-dimensional object.
[0133] Since no mechanical release of a release layer is required,
or no mechanical movement of a build surface to replenish oxygen is
required, the method can be carried out in a continuous fashion,
though it will be appreciated that the individual steps noted above
may be carried out sequentially, concurrently, or a combination
thereof. Indeed, the rate of steps can be varied over time
depending upon factors such as the density and/or complexity of the
region under fabrication.
[0134] Also, since mechanical release from a window or from a
release layer generally requires that the carrier be advanced a
greater distance from the build plate than desired for the next
irradiation step, which enables the window to be recoated, and then
return of the carrier back closer to the build plate (e.g., a "two
steps forward one step back" operation), the present invention in
some embodiments permits elimination of this "back-up" step and
allows the carrier to be advanced unidirectionally, or in a single
direction, without intervening movement of the window for
re-coating, or "snapping" of a pre-formed elastic release-layer.
However, in other embodiments of the invention, reciprocation is
utilized not for the purpose of obtaining release, but for the
purpose of more rapidly filling or pumping polymerizable liquid
into the build region.
[0135] In some embodiments, the advancing step is carried out
sequentially in uniform increments (e.g., of from 0.1 or 1 microns,
up to 10 or 100 microns, or more) for each step or increment. In
some embodiments, the advancing step is carried out sequentially in
variable increments (e.g., each increment ranging from 0.1 or 1
microns, up to 10 or 100 microns, or more) for each step or
increment. The size of the increment, along with the rate of
advancing, will depend in part upon factors such as temperature,
pressure, structure of the article being produced (e.g., size,
density, complexity, configuration, etc.)
[0136] In other embodiments of the invention, the advancing step is
carried out continuously, at a uniform or variable rate.
[0137] In some embodiments, the rate of advance (whether carried
out sequentially or continuously) is from about 0.1 1, or 10
microns per second, up to about to 100, 1,000, or 10,000 microns
per second, again depending again depending on factors such as
temperature, pressure, structure of the article being produced,
intensity of radiation, etc
[0138] As described further below, in some embodiments the filling
step is carried out by forcing said polymerizable liquid into said
build region under pressure. In such a case, the advancing step or
steps may be carried out at a rate or cumulative or average rate of
at least 0.1, 1, 10, 50, 100, 500 or 1000 microns per second, or
more. In general, the pressure may be whatever is sufficient to
increase the rate of said advancing step(s) at least 2, 4, 6, 8 or
10 times as compared to the maximum rate of repetition of said
advancing steps in the absence of said pressure. Where the pressure
is provided by enclosing an apparatus such as described above in a
pressure vessel and carrying the process out in a pressurized
atmosphere (e.g., of air, air enriched with oxygen, a blend of
gasses, pure oxygen, etc.) a pressure of 10, 20, 30 or 40 pounds
per square inch (PSI) up to, 200, 300, 400 or 500 PSI or more, may
be used. For fabrication of large irregular objects higher
pressures may be less preferred as compared to slower fabrication
times due to the cost of a large high pressure vessel. In such an
embodiment, both the feed surface and the polymerizable liquid can
be in fluid contact with the same compressed gas (e.g., one
comprising from 20 to 95 percent by volume of oxygen, the oxygen
serving as the polymerization inhibitor.
[0139] On the other hand, when smaller items are fabricated, or a
rod or fiber is fabricated that can be removed or exited from the
pressure vessel as it is produced through a port or orifice
therein, then the size of the pressure vessel can be kept smaller
relative to the size of the product being fabricated and higher
pressures can (if desired) be more readily utilized.
[0140] As noted above, the irradiating step is in some embodiments
carried out with patterned irradiation. The patterned irradiation
may be a fixed pattern or may be a variable pattern created by a
pattern generator (e.g., a DLP) as discussed above, depending upon
the particular item being fabricated.
[0141] When the patterned irradiation is a variable pattern rather
than a pattern that is held constant over time, then each
irradiating step may be any suitable time or duration depending on
factors such as the intensity of the irradiation, the presence or
absence of dyes in the polymerizable material, the rate of growth,
etc. Thus in some embodiments each irradiating step can be from
0.001, 0.01, 0.1, 1 or 10 microseconds, up to 1, 10, or 100
minutes, or more, in duration. The interval between each
irradiating step is in some embodiments preferably as brief as
possible, e.g., from 0.001, 0.01, 0.1, or 1 microseconds up to 0.1,
1, or 10 seconds.
[0142] While the dead zone and the gradient of polymerization zone
do not have a strict boundary therebetween (in those locations
where the two meet), the thickness of the gradient of
polymerization zone is in some embodiments at least as great as the
thickness of the dead zone. Thus, in some embodiments, the dead
zone has a thickness of from 0.01, 0.1, 1, 2, or 10 microns up to
100, 200 or 400 microns, or more, and/or said gradient of
polymerization zone and said dead zone together have a thickness of
from 1 or 2 microns up to 400, 600, or 1000 microns, or more. Thus
the gradient of polymerization zone may be thick or thin depending
on the particular process conditions at that time. Where the
gradient of polymerization zone is thin, it may also be described
as an active surface on the bottom of the growing three-dimensional
object, with which monomers can react and continue to form growing
polymer chains therewith. In some embodiments, the gradient of
polymerization zone, or active surface, is maintained (while
polymerizing steps continue) for a time of at least 5, 10, 15, 20
or 30 seconds, up to 5, 10, 15 or 20 minutes or more, or until
completion of the three-dimensional product.
[0143] The method may further comprise the step of disrupting said
gradient of polymerization zone/active surface, for a time
sufficient to form a cleavage line in said three-dimensional object
(e.g., at a predetermined desired location for intentional
cleavage, or at a location in said object where prevention of
cleavage or reduction of cleavage is non-critical), and then
reinstating said gradient of polymerization zone (e.g. by pausing,
and resuming, the advancing step, increasing, then decreasing, the
intensity of irradiation, and combinations thereof.
[0144] In some embodiments the build surface is flat; in other the
build surface is irregular such as convexly or concavely curved, or
has walls or trenches formed therein. In either case the build
surface may be smooth or textured.
[0145] Curved and/or irregular build plates or build surfaces can
be used in fiber or rod formation, to provide different materials
to a single object being fabricated (that is, different
polymerizable liquids to the same build surface through channels or
trenches formed in the build surface, each associated with a
separate liquid supply, etc.
[0146] Carrier Feed Channels for Polymerizable liquid. While
polymerizable liquid may be provided directly to the build plate
from a liquid conduit and reservoir system, in some embodiments the
carrier include one or more feed channels therein. The carrier feed
channels are in fluid communication with the polymerizable liquid
supply, for example a reservoir and associated pump. Different
carrier feed channels may be in fluid communication with the same
supply and operate simultaneously with one another, or different
carrier feed channels may be separately controllable from one
another (for example, through the provision of a pump and/or valve
for each). Separately controllable feed channels may be in fluid
communication with a reservoir containing the same polymerizable
liquid, or may be in fluid communication with a reservoir
containing different polymerizable liquids. Through the use of
valve assemblies, different polymerizable liquids may in some
embodiments be alternately fed through the same feed channel, if
desired.
5. Reciprocating Feed of Polymerizable Liquid.
[0147] In an embodiment of the present invention, the carrier is
vertically reciprocated (or oscillated) with respect to the build
surface (that is, the two are vertically reciprocated with respect
to one another) to enhance or speed the refilling of the build
region with the polymerizable liquid. Such reciprocations or
oscillations (these two terms being used interchangeably herein)
may be of any suitable configuration, including uniform and
non-uniform, and/or periodic or non-periodic, with respect to one
another, so long as they are configured to enhance feed of the
polymerizable liquid to the build surface.
[0148] In some embodiments, the vertically reciprocating step,
which comprises an upstroke and a downstroke, is carried out with
the distance of travel of the upstroke being greater than the
distance of travel of the downstroke, to thereby concurrently carry
out the advancing step (that is, driving the carrier away from the
build plate in the Z dimension) in part or in whole.
[0149] In some embodiments, the speed of the upstroke gradually
accelerates (that is, there is provided a gradual start and/or
gradual acceleration of the upstroke, over a period of at least 20,
30, 40, or 50 percent of the total time of the upstroke, until the
conclusion of the upstroke, or the change of direction which
represents the beginning of the downstroke. Stated differently, the
upstroke begins, or starts, gently or gradually.
[0150] In some embodiments, the speed of the downstroke gradually
decelerates (that is, there is provided a gradual termination
and/or gradual deceleration of the downstroke, over a period of at
least 20, 30, 40, or 50 percent of the total time of the
downstroke. Stated differently, the downstroke concludes, or ends,
gently or gradually.
[0151] While in some embodiments there is an abrupt end, or abrupt
deceleration, of the upstroke, and an abrupt beginning or
acceleration of the downstroke (e.g., a rapid change in vector or
direction of travel from upstroke to downstroke), it will be
appreciated that gradual transitions may be introduced here as well
(e.g., through introduction of a "plateau" or pause in travel
between the upstroke and downstroke). It will also be appreciated
that, while each reciprocating step may be consist of a single
upstroke and downstroke, the reciprocation step may comprise a
plurality of 2, 3, 4 or 5 or more linked set of reciprocations,
which may e the same or different in frequent and/or amplitude
[0152] In some embodiments, the vertically reciprocating step is
carried out over a total time of from 0.01 or 0.1 seconds up to 1
or 10 seconds (e.g., per cycle of an upstroke and a
downstroke).
[0153] In some embodiments, the upstroke distance of travel is from
0.02 or 0 2 millimeters (or 20 or 200 microns) to 1 or 10
millimeters (or 1000 to 10,000 microns). The distance of travel of
the downstroke may be the same as, or less than, the distance of
travel of the upstroke, where a lesser distance of travel for the
downstroke serves to achieve the advancing of the carrier away from
the build surface as the three-dimensional object is gradually
formed. Where a reciprocation step comprises multiple linked
reciprocations, the sum distance of travel of all upstrokes in that
set is preferably greater than the sum distance of travel of all
downstrokes in that set, to achieve the advancing of the carrier
away from the build surface as the three-dimensional object is
gradually formed.
[0154] Preferably the vertically reciprocating step, and
particularly the upstroke thereof, does not cause the formation of
gas bubbles or a gas pocket in the build region, but instead the
build region remains filled with the polymerizable liquid
throughout the reciprocation steps, and the gradient of
polymerization zone or region remains in contact with the "dead
zone" and with the growing object being fabricated throughout the
reciprocation steps. As will be appreciated, a purpose of the
reciprocation is to speed or enhance the refilling of the build
region, particularly where larger build regions are to be refilled
with polymerizable liquid, as compared to the speed at which the
build region could be refilled without the reciprocation step.
[0155] In some embodiments, the advancing step is carried out
intermittently at a rate of 1, 2, 5 or 10 individual advances per
minute up to 300, 600, or 1000 individual advances per minute, each
followed by a pause during which an irradiating step is carried
out. It will be appreciated that one -or more reciprocation steps
(e.g., upstroke plus downstroke) may be carried out within each
advancing step. Stated differently, the reciprocating steps may be
nested within the advancing steps.
[0156] In some embodiments, the individual advances are carried out
over an average distance of travel for each advance of from 10 or
50 microns to 100 or 200 microns (optionally including the total
distance of travel for each vertically reciprocating step, e.g.,
the sum of the upstroke distance minus the downstroke
distance).
[0157] Apparatus for carrying out the invention in which the
reciprocation steps described herein are implemented substantially
as described above, with the drive associated with the carrier,
and/or with an additional drive operatively associated with the
transparent member, and with the controller operatively associated
with either or both thereof and configured to reciprocate the
carrier and transparent member with respect to one another as
described above.
[0158] In the alternative, vertical reciprocation may be carried
out by configuring the build surface (and corresponding build
plate) so that it may have a limited range of movement up and down
in the vertical or "Z" dimension, while the carrier advances (e.g.,
continuously or step-wise) away from the build plate in the
vertical or "Z" dimension. In some embodiments, such limited range
of movement may be passively imparted, such as with upward motion
achieved by partial adhesion of the build plate to the growing
object through a viscous polymerizable liquid, followed by downward
motion achieved by the weight, resiliency, etc. of the build plate
(optionally including springs, buffers, shock absorbers or the
like, configured to influence either upward or downward motion of
the build plate and build surface). In another embodiment, such
motion of the build surface may be actively achieved, by
operatively associating a separate drive system with the build
plate, which drive system is also operatively associated with the
controller, to separately achieve vertical reciprocation. In still
another embodiment, vertical reciprocation may be carried out by
configuring the build plate, and/or the build surface, so that it
flexes upward and downward, with the upward motion thereof being
achieved by partial adhesion of the build surface to the growing
object through a viscous polymerizable liquid, followed by downward
motion achieved by the inherent stiffness of the build surface
biasing it or causing it to return to a prior position.
[0159] It will be appreciated that illumination or irradiation
steps, when intermittent, may be carried out in a manner
synchronized with vertical reciprocation, or not synchronized with
vertical reciprocation, depending on factors such as whether the
reciprocation is achieved actively or passively.
[0160] It will also be appreciated that vertical reciprocation may
be carried out between the carrier and all regions of the build
surface simultaneously (e.g., where the build surface is rigid), or
may be carried out between the carrier and different regions of the
build surface at different times (e.g., where the build surface is
of a flexible material, such as a tensioned polymer film).
6. Increased Speed of Fabrication by Increasing Light
Intensity.
[0161] In general, it has been observed that speed of fabrication
can increase with increased light intensity. In some embodiments,
the light is concentrated or "focused" at the build region to
increase the speed of fabrication. This may be accomplished using
an optical device such as an objective lens.
[0162] The speed of fabrication may be generally proportional to
the light intensity. For example, the build speed in millimeters
per hour may be calculated by multiplying the light intensity in
milliWatts per square centimeter and a multiplier. The multiplier
may depend on a variety of factors, including those discussed
below. A range of multiplers, from low to high, may be employed. On
the low end of the range, the multiplier may be about 10, 15, 20 or
30. On the high end of the mutipler range, the multiplier may be
about 150, 300, 400 or more.
[0163] The relationships described above are, in general,
contemplated for light intensities of from 1, 5 or 10 milliWatts
per square centimeter, up to 20 or 50 milliWatts per square
centimeter.
[0164] Certain optical characteristics of the light may be selected
to facilitate increased speed of fabrication. By way of example, a
band pass filter may be used with a mercury bulb light source to
provide 365.+-.10 nm light measured at Full Width Half Maximum
(FWHM). By way of further example, a band pass filter may be used
with an LED light source to provide 375.+-.15 nm light measured at
FWHM.
[0165] As noted above, poymerizable liquids used in such processes
are, in general, free radical polymerizable liquids with oxygen as
the inhibitor, or acid-catalyzed or cationically polymerizable
liquids with a base as the inhibitor. Some specific polymerizable
liquids will of course cure more rapidly or efficiently than others
and hence be more amenable to higher speeds, though this may be
offset at least in part by further increasing light intensity.
[0166] At higher light intensities and speeds, the "dead zone" may
become thinner as inhibitor is consumed. If the dead zone is lost
then the process will be disrupted. In such case, the supply of
inhibitor may be enhanced by any suitable means, including
providing an enriched and/or pressurized atmosphere of inhibitor, a
more porous semipermeable member, a stronger or more powerful
inhibitor (particularly where a base is employed), etc.
[0167] In general, lower viscosity polymerizable liquids are more
amenable to higher speeds, particularly for fabrication of articles
with a large and/or dense cross section (although this can be
offset at least in part by increasing light intensity).
Polymerizable liquids with viscosities in the range of 50 or 100
centipoise, up to 600, 800 or 1000 centipoise or more (as measured
at room temperature and atmospheric pressure with a suitable device
such as a HYDRAMOTION REACTAVISC.TM. Viscometer (available from
Hydramotion Ltd, 1 York Road Business Park, Mallon, York Y017 6YA
England). In some embodiments, where necessary, the viscosity of
the polymerizable liquid can advantageously be reduced by heating
the polymerizable liquid, as described above.
[0168] In some embodiments, such as fabrication of articles with a
large and/or dense cross-section, speed of fabrication can be
enhanced by introducing reciprocation to "pump" the polymerizable
liquid, as described above, and/or the use of feeding the
polymerizable liquid through the carrier, as also described above,
and/or heating and/or pressurizing the polymerizable liquid, as
also described above.
7. Tiling.
[0169] It may be desirable to use more than one light engine to
preserve resolution and light intensity for larger build sizes.
Each light engine may be configured to project an image (e.g., an
array of pixels) into the build region such that a plurality of
"tiled" images are projected into the build region. As used herein,
the term "light engine" can mean an assembly including a light
source, a DLP device such as a digital micromirror device and an
optical device such as an objective lens. The "light engine" may
also include electronics such as a controller that is operatively
associated with one or more of the other components.
[0170] In some embodiments, a configuration with the overlapped
images is employed with some form of "blending" or "smoothing" of
the overlapped regions as generally discussed in, for example, U.S.
Pat. Nos. 7,292,207, 8,102,332, 8,427,391, 8,446,431 and U.S.
Patent Application Publication Nos. 2013/0269882, 2013/0278840 and
2013/0321475, the disclosures of which are incorporated herein in
their entireties.
[0171] The tiled images can allow for larger build areas without
sacrificing light intensity, and therefore can facilitate faster
build speeds for larger objects. It will be understood that more
than two light engine assemblies (and corresponding tiled images)
may be employed. Various embodiments of the invention employ at
least 4, 8, 16, 32, 64, 128 or more tiled images.
8. Fabrication in Multiple Zones.
[0172] As noted above, embodiments of the invention may carry out
the formation of the three-dimensional object through multiple
zones or segments of operation. Such a method generally
comprises:
[0173] (a) providing a carrier and an optically transparent member
having a build surface, the carrier and the build surface defining
a build region therebetween, with the carrier positioned adjacent
and spaced apart from the build surface at a start position;
then
[0174] (b) forming an adhesion segment of the three-dimensional
object by: [0175] (i) filling the build region with a polymerizable
liquid, [0176] (ii) irradiating the build region with light through
the optically transparent member (e.g., by a single exposure),
while [0177] (iii) maintaining the carrier stationary or advancing
the carrier away from the build surface at a first cumulative rate
of advance, to thereby form from the polymerizable liquid a solid
polymer adhesion segment of the object adhered to the carrier;
then
[0178] (c) optionally but preferably forming a transition segment
of the three dimensional object by [0179] (i) filling the build
region with a polymerizable liquid, [0180] (ii) continuously or
intermittently irradiating the build region with light through the
optically transparent member, and [0181] (iii) continuously or
intermittently advancing (e.g., sequentially or concurrently with
the irradiating step) the carrier away from the build surface at a
second cumulative rate of advance to thereby form from the
polymerizable liquid a transition segment of the object between the
adhesion segment and the build surface; [0182] wherein the second
cumulative rate of advance is greater than the first cumulative
rate of advance; and then
[0183] (d) forming a body segment of the three dimensional object
by: [0184] (i) filling the build region with a polymerizable
liquid, [0185] (ii) continuously or intermittently irradiating the
build region with light through the optically transparent, and
[0186] (iii) continuously or intermittently advancing (e.g.,
sequentially or concurrently with the irradiating step) the carrier
away from the build surface at a third cumulative rate of advance,
to thereby form from the polymerizable liquid a body segment of the
object between the transition segment and the build surface; [0187]
wherein the third cumulative rate of advance is greater than the
first and/or the second cumulative rate of advance.
[0188] Note that the start position can be any position among a
range of positions (e.g., a range of up to 5 or 10 millimeters or
more), and the irradiating step (b)(ii) is carried out at an
intensity sufficient to adhere the solid polymer to the carrier
when the carrier is at any position within that range of positions.
This advantageously reduces the possibility of failure of adhesion
of the three-dimensional object to the carrier due to variations in
uniformity of the carrier and/or build surfaces, variations
inherent in drive systems in positioning the carrier adjacent the
build surface, etc.
[0189] 9. Fabrication with Intermittent (or Strobe")
Illumination.
[0190] As noted above, in some embodiments the invention may be
carried out with the illumination in intermittent periods or burst.
In one embodiment, such a method comprises:
[0191] providing a carrier and an optically transparent member
having a build surface, the carrier and the build surface defining
a build region therebetween;
[0192] filling the build region with a polymerizable liquid,
[0193] intermittently irradiating the build region with light
through the optically transparent member to form a solid polymer
from the polymerizable liquid,
[0194] continuously advancing the carrier away from the build
surface to form the three-dimensional object from the solid
polymer.
[0195] Another embodiment of such a mode of operation
comprises:
[0196] providing a carrier and an optically transparent member
having a build surface, the carrier and the build surface defining
a build region therebetween;
[0197] filling the build region with a polymerizable liquid,
[0198] intermittently irradiating the build region with light
through the optically transparent member to form a solid polymer
from the polymerizable liquid,
[0199] continuously or intermittently advancing (e.g., sequentially
or concurrently with the irradiating step) the carrier away from
the build surface to form the three-dimensional object from the
solid polymer.
[0200] In some embodiments, the intermittently irradiating
comprises alternating periods of active and inactive illumination,
where the average duration of the periods of active illumination is
less than the average duration of the periods of inactive
illumination (e.g., is not more than 50, 60, or 80 percent
thereof).
[0201] In other embodiments, the intermittently irradiating
comprises alternating periods of active and inactive illumination,
where the average duration of the periods of active illumination is
the same as or greater than the average duration of the periods of
inactive illumination (e.g., is at least 100, 120, 160, or 180
percent thereof).
[0202] Examples of such modes of operation are given further below.
These features may be combined with any of the other features and
operating steps or parameters described herein.
10. Fabrication of Body Segment by Multiple Operating Modes.
[0203] Operating modes (that is, the pattern defining the manner of
irradiating and advancing) may be changed in the course of
fabricating a three dimensional object (i.e., the major portion, or
"body portion", thereof), to best suit the particular geometry of
each contiguous segment of that three-dimensional object,
particularly as that geometry changes during the course of
fabrication.
[0204] In general, base and transition zones may still be
fabricated as described above, as the preferred foundation for the
body of that object during fabrication thereof.
[0205] Horizontal portions of the three, dimensional object, abrupt
changes in cross section, and converging or diverging elements of
the three dimensional object, may be fabricated in a reciprocal or
oscillatory operating mode, for example, to eliminate surface
defects, such as pitting, and speed or enhance resin replenishment
to the build region.
[0206] Vertical and thin-walled sections of the three dimensional
object, and fragile elements or fine features thereof, can be
fabricated in a continuous operating mode. In some embodiments,
continuous mode is least concussive of the various operating modes,
and hence is better suited to fabricating segments of
three-dimensional objects with complex or delicate geometries
(though this may be influenced by the choice of materials for the
build surface--that is, rigid vs. flexible).
[0207] Feathering, or gradual transitioning of operating mode
parameters, may be included in the course of changing operating
modes (that is, between one operating mode and a subsequent
operating mode). For example, in an intra-oscillatory build:
oscillatory parameters are driven by enabling resin flow and allow
time for the resin level in the build area to equilibrate--for
thinner cross-sections, one can use a lower oscillation height,
faster oscillation speeds, and/or smaller delay time to replenish
resin, while the opposite is true for thicker cross-sections.
[0208] In feathering from an reciprocal (or oscillatory) to
continuous operating mode: A pause following oscillatory mode, ramp
in continuous speed from 10 mm/hr to standard continuous speed as
analog to transition zone, effective dosage to initial slices drops
from "over-exposed" (allowing proper adhesion) to the recommended
dosage.
[0209] In feathering from continuous to oscillatory: initial
oscillation displacement following transition accounts for area of
last exposed continuous frame, e.g. high oscillation displacement
for large cross-section and vice versa. Dosage for initial frames
can be constant or ramped from high to low.
[0210] In an alternative to changing operating modes (or in
combination with changing operating modes), the parameters of an
operating mode can be changed during formation of the
three-dimensional object. Examples of parameters that can be
changed include, for example, frequency of irradiating, intensity
of irradiating, duration of irradiating, duty cycle of irradiating,
rate of advancing, lead time prior to irradiating, lag time
following irradiating, step height, pump height, step or pump
duration, or frequency of step-wise or reciprocal advancing. For
example:
[0211] greater pump height may be preferred for fabricating a dense
portion or segments of an object (such as a completely solid
portion, or a dense foam or lattice portion);
[0212] greater pump speed may be preferred for a sparse (or less
dense) segment or portion of an object, such as a hollow,
mesh-filled, open foam or open lattice portion of an object;
and
[0213] decreased lead and lag times may be preferred when overall
speed or rate of formation is increased.
Additional reasons for varying such parameters are indicated above
and below.
[0214] It will be appreciated that the pattern of exposure may be
changed in the course of fabrication, e.g., from slice to slice, to
alter the geometry of external surfaces of the three-dimensional
object, to alter the geometry of internal surfaces of the three
dimensional object for structural purposes, to alter the geometry
of internal surfaces of the object to change micro-structure or
material properties of the object (e.g., in the formation of a
regular or irregular mesh, lattice, or foam (including open and
closed cell foams), to maintain or alter flow of the polymerizable
liquid to the build region, etc. In addition, in the present
invention, slice thickness may advantageously be varied, as
discussed further below.
11. Varying Slice Thickness.
[0215] As noted above, the methods and processes described herein
advantageously accommodate input in varying slice thickness, rather
than a fixed slice thickness, during formation of a
three-dimensional object, allowing the operation of the methods and
apparatus to be simplified, and particularly for electronic or
computer-generated instructions to the apparatus for carrying out
the method to be simplified. For example, for an object that
includes both finely detailed portions as well as less detailed
portions, or relatively constant portions, slice thickness can be
thinner for the detailed portions, and thicker for the relatively
constant portions.
[0216] The number of times slice thickness is changed will depend
upon factors such as the object material and properties, geometry,
tensile or other material properties, tolerances, etc. There are no
particular limits, and hence in some embodiments, slice thickness
may be changed at least 2, 4, 8 or 10 times during formation of the
object or object body portion (and optionally up to 100 or 1000
times, or more). Note that every change may not be to a different
slice thickness, but may in some instances be a reversion to a
previous (but not the immediately previous) slice thickness.
[0217] For example, in some embodiments, changing may be between:
at least one slice having a thickness of less than 2 or 4 microns;
optionally at least one slice having a thickness between 40 and 80
microns; and at least one slice having a thickness of more than
200, 400 or 600 microns.
[0218] In some embodiments, changing may be between: at least one
slice having a thickness of less than 2 or 4 microns; and at least
one slice having a thickness of more than 40 or 80 microns.
[0219] In some embodiments, the changing may be between at least
one slice having a thickness of less than 20 or 40 microns;
optionally at least one slice having a thickness between 60 and 80
microns; and at least one slice having a thickness of more than
200, 400, or 600 microns.
[0220] In some embodiments, the changing may be between at least a
first thin slice and a second thicker slice, wherein said second
slice has a thickness at least 5, 10, 15 or 20 times greater than
said first slice.
[0221] In some embodiments, the changing is between at least a
first plurality (e.g., at least 2, 5, 10 or 20) of contiguous thin
slices and a second thicker slice, wherein each of said thin slices
is different from one another, and wherein said second thicker
slice has a thickness at least 5, 10, 15, or 20 times greater than
each of said plurality of thin slices.
[0222] Variation of slice thickness may be implemented in any
operating mode, as discussed further below, and in combination with
changing operating modes in the course of fabricating a particular
three-dimensional object, as also discussed further below.
12. Fabrication Products.
[0223] Three-dimensional products produced by the methods and
processes of the present invention may be final, finished or
substantially finished products, or may be intermediate products
subject to further manufacturing steps such as surface treatment,
laser cutting, electric discharge machining, etc., is intended.
Intermediate products include products for which further additive
manufacturing, in the same or a different apparatus, may be carried
out). For example, a fault or cleavage line may be introduced
deliberately into an ongoing "build" by disrupting, and then
reinstating, the gradient of polymerization zone, to terminate one
region of the finished product, or simply because a particular
region of the finished product or "build" is less fragile than
others.
[0224] Numerous different products can be made by the methods and
apparatus of the present invention, including both large-scale
models or prototypes, small custom products, miniature or
microminiature products or devices, etc. Examples include, but are
not limited to, medical devices and implantable medical devices
such as stents, drug delivery depots, functional structures,
microneedle arrays, fibers and rods such as waveguides,
micromechanical devices, microfluidic devices, etc.
[0225] Thus in some embodiments the product can have a height of
from 0.1 or 1 millimeters up to 10 or 100 millimeters, or more,
and/or a maximum width of from 0.1 or 1 millimeters up to 10 or 100
millimeters, or more. In other embodiments, the product can have a
height of from 10 or 100 nanometers up to 10 or 100 microns, or
more, and/or a maximum width of from 10 or 100 nanometers up to 10
or 100 microns, or more. These are examples only: Maximum size and
width depends on the architecture of the particular device and the
resolution of the light source and can be adjusted depending upon
the particular goal of the embodiment or article being
fabricated.
[0226] In some embodiments, the ratio of height to width of the
product is at least 2:1, 10:1, 50:1, or 100:1, or more, or a width
to height ratio of 1:1, 10:1, 50:1, or 100:1, or more.
[0227] In some embodiments, the product has at least one, or a
plurality of, pores or channels formed therein, as discussed
further below.
[0228] The processes described herein can produce products with a
variety of different properties. Hence in some embodiments the
products are rigid; in other embodiments the products are flexible
or resilient. In some embodiments, the products are a solid; in
other embodiments, the products are a gel such as a hydrogel. In
some embodiments, the products have a shape memory (that is, return
substantially to a previous shape after being deformed, so long as
they are not deformed to the point of structural failure). In some
embodiments, the products are unitary (that is, formed of a single
polymerizable liquid); in some embodiments, the products are
composites (that is, formed of two or more different polymerizable
liquids). Particular properties will be determined by factors such
as the choice of polymerizable liquid(s) employed.
[0229] In some embodiments, the product or article made has at
least one overhanging feature (or "overhang"), such as a bridging
element between two supporting bodies, or a cantilevered element
projecting from one substantially vertical support body. Because of
the unidirectional, continuous nature of some embodiments of the
present processes, the problem of fault or cleavage lines that form
between layers when each layer is polymerized to substantial
completion and a substantial time interval occurs before the next
pattern is exposed, is substantially reduced. Hence, in some
embodiments the methods are particularly advantageous in reducing,
or eliminating, the number of support structures for such overhangs
that are fabricated concurrently with the article.
13. Additional Build Plate Materials
[0230] Any suitable material may be used to form the build plates
described herein, including multi-layer build plates and/or build
plates formed of more than one material. For example, the flexible
layer (used alone or with additional supports or layers) may
include a woven glass fabric (fiberglass or e-glass) with a
crosslinked silicone elastomeric coating (such as room temperature
vulcanized (RTV) silicone), which may be lightly infiltrated into
the glass fiber fabric to provide mechanical durability. The oxygen
permeability of silicone elastomer (rubber) is similar to
Teflon.RTM. AF-2400. Such a configuration may be used alone or
affixed (adhesively adhered) to a glass plate with the unfilled
areas of the fabric available for air (oxygen) flow. Sulfonated
tetrafluoroethylene based fluoropolymer-copolymers, such as
Nafion.RTM. from Dupont may also be used.
[0231] In some embodiments, asymmetric flat sheet membranes which
are currently used in very high quantity for water purification
applications (see U.S. Patent Publication No. 2014/0290478) may be
used. These membranes are generally polysulfone or
polyethersulfone, and may be coated with perfluoropolymers or
crosslinked silicone elastomer to increase chemical resistance.
Also poly(vinylidene fluoride) and possibly polyimide asymmetric
(porous) membranes may be used, for example, if chemical resistance
is a problem. Some of the membranes may be used as is without
coatings. Examples of such membranes include FilmTec.RTM. membranes
(Dow Chemical, Midland, Mich. (USA)). These are porous polysulfone
asymmetric membranes coated with a crosslinked high Tg polyamide
(with a coating thickness of about 0.1 microns). The crosslinked
polyamide coating should provide chemical resistance. Although the
oxygen permeability of the polyamide is low, the thickness of the
coating may be so low that the effective oxygen transmission rate
is high. The polysulfone support without the polyamide layer could
be coated with a wide variety of polymers such as silicone rubber
(or AF-2400) to yield very high oxygen transmission. The
FilmTec.RTM. membranes are produced in very high quantity as they
are the prime material used in water desalination plants. PVDF
porous membranes may allow repeated use.
14. Additional Build Plate Materials
[0232] In some embodiments, enrichment of the atmosphere with a
polymerization inhibitor, such as oxygen, may be used. For example,
an oxygen enriched source may be used, for example, to maintain a
high oxygen partial pressure despite a reduced total gas pressure
under the build plate or to enable less permeable build windows
while still permitting sufficient oxygen or other polymerization
inhibitor to be present in the build region.
15. Buildplate Coatings
[0233] Omniphobic surfaces may be used on the build plate surface
or build region. For example, patterned surfaces (either a random
array of particles or mircro patterned surfaces) that contain
non-miscible fluids that are pinned or held to the surface by
capillary forces may be used. Such a surface may result in fluid on
the surface floating along the surface. Examples of such surfaces
are described in U.S. Pat. Nos. 8,535,779 and 8,574,704, the
disclosures of which are hereby incorporated by reference in their
entireties.
16. Build Plate Flexible Layers
[0234] Although embodiments according to the present invention are
described with respect to flexible layers on the build plate that
include a semipermeable (or gas permeable) member (e.g.,
perfluoropolymers, such as TEFLON AF.RTM. fluoropolymers, it should
be understood that any suitable flexible material may be used,
either alone (with a tensioning member or "drum head"
configuration) or placed on top of another, strengthening
substrate, such as class. For example, a transparent, resilient
paper, such as glassine, may be used. Glassine is a relatively
transparent, greaseproof paper formed of well-hydrated cellulosic
fibers that has been super calendared. Glassine may be plasticized
and/or coated with wax or a glaze. Glassine may be gas permeable.
In some embodiments, the glassine may be coated with a thin layer
of crosslinked silicone elastomer or a perfluoropolymer, such as
TEFLON AF.RTM. fluoropolymers. Glassine paper is substantially
grease resistant, and may have limited adhesion to the
polymerizable liquid described herein.
17. Build Plates having Lighting Panels
[0235] FIG. 2 illustrates a 3D printing device with a digital light
processing (DLP) system as a light source, however, in some
embodiments, lighting panel light sources may be used. In
particular, a bottom layer of the build plate, such as the base
layer in the build plates shown in FIG. 22-25, may be used as a
display screen of a lighting panel to irradiate resin in the build
region. For example, as illustrated in FIG. 22-23, the base layer
of the build plate formed may be used to form a screen of a
lighting panel. In some embodiments, the base layer may be omitted,
and the lighting panel may provide similar functionality and
support as the base layer. As illustrated in FIGS. 24-25, a
lighting panel 900 may be positioned on the bottom portion of a
base layer and be connected to a light source controller 950.
[0236] As illustrated in FIGS. 22-23, a build plate may include a
lighting panel, a base layer, an adhesive layer and a permeable
sheet. Channels may be formed in the permeable sheet (FIG. 22) or
in the base layer (FIG. 23) to increase oxygen flow to the build
surface. According to some embodiments, the build plate may be
configured to allow a polymerization inhibitor to reach the build
surface. In particular, the build plate includes a rigid, optically
transparent, gas-impermeable planar base having upper and lower
surfaces, and an optically transparent sheet having upper and lower
surfaces such that the sheet lower surface is positioned on the
base upper surface. The base upper surface and/or the sheet lower
surface have a surface topology that increases gas flow to the gas
permeable sheet. For example, the surface topology may include a
surface roughness (a random "rough" surface or a pattern of
features or channels) that maintains a sufficient gap between the
base and the sheet such that a polymerization inhibitor may flow
through the gap through the permeable sheet and to the build
surface. In some embodiments, the surface topology may reduce or
prevent surface wetting or sticking between the base and the sheet.
In this configuration, a relatively thin, flexible permeable sheet
may be used. The rigid base may serve to stabilize the flexible
sheet and/or reduce or prevent warping or bowing, particularly in
the lower direction, during three-dimensional object fabrication.
The surface topology may be configured to sufficiently maintain an
optical pathway of radiation passing through the window (e.g., by
limiting any optical blocking or scattering) so as to minimize any
effects on the resolution of the three-dimensional object
fabrication. The sheet may be held against the plate by one or more
clamps along the periphery or a "drum head" configuration. The
surface a rougher surface would typically result in greater
scattering angles than a smoother surface. In some embodiments, the
optical scattering angle at all points along the longitudinal area
of the sheet (e.g., due to the uneven surface topology of the
channels or other features) is less than 20%, 10%, 5.0% or
1.0%.
[0237] The rigid base and flexible sheet can be made of any
suitable material that is optically transparent at the relevant
wavelengths (or otherwise transparent to the radiation source,
whether or not it is visually transparent as perceived by the human
eye--i.e., an optically transparent window may in some embodiments
be visually opaque). In some embodiments, the rigid base is
impermeable with respect to the polymerization inhibitor.
[0238] In some embodiments, the flexible sheet may be formed from a
thin film or sheet of material which is flexible when separated
from the apparatus of the invention, but which is clamped and
tensioned when installed in the apparatus (e.g., with a tensioning
ring) so that it is rendered rigid in the apparatus. Polymer films
are preferably fluoropolymer films, such as an amorphous
thermoplastic fluoropolymer, in a thickness of 0.01 or 0.05
millimeters to 0.1 or 1 millimeters, or more. In some embodiments,
Biogeneral Teflon AF 2400 polymer film, which is 0.0035 inches
(0.09 millimeters) thick, and Random Technologies Teflon AF 2400
polymer film, which is 0.004 inches (0.1 millimeters) thick may be
used. Tension on the film is preferably adjusted with a tension
ring to about 10 to 100 pounds, depending on operating conditions
such as fabrication speed.
[0239] Particular materials include TEFLON AF.RTM. fluoropolymers,
commercially available from DuPont. Additional materials include
perfluoropolyether polymers such as described in U.S. Pat. Nos.
8,268,446; 8,263,129; 8,158,728; and 7,435,495. For example, the
sheet may include an amorphous thermoplastic fluoropolymer like
TEFLON AF 1600.TM. or TEFLON AF 2400.TM. fluoropolymer films, or
perfluoropolyether (PFPE), particularly a crosslinked PFPE film, or
a crosslinked silicone polymer film. Many other materials are also
possible to use, as long as the flux of the polymerization
inhibitor is adequate to attenuate the photo-polymerization to
create the dead zone. Other materials could include semicrystalline
fluoropolymers, such as thin films (10-50 microns thick) of
fluorinated ethylene propylene (FEP), paraformaldehyde (PFA),
polyvinylidene fluoride (PVDF) or other materials known in the art.
The permeability of these materials (FEP, PFA, PVDF) to the
polymerization inhibitor oxygen may be lower than TEFLON AF, but
with the attenuation of oxygen concentration, oxygen pressure,
temperature, and light characteristics (wavelength, intensity),
adequate creation of the dead zone may be achieved.
[0240] The adhesive layers described herein may be a gas-permeable
adhesive, such as a poly(dimethylsiloxane) (PDMS) film (e.g., as a
silicone transfer film adhesive that can be applied using a
polyester release liner, such as ARseal.TM.8026 (Adhesives
Research, Glen Rock, Pa. (USA)). The adhesive layer is preferably
an adhesive that is both gas-permeable and has good adhesive
qualities with respect to the material of the base (e.g., glass,
silicone, quartz, sapphire, polymer materials) and the material of
the sheet (e.g., polymers described below). In this configuration,
air flow may be permitted through the uneven surface topology
(channels) of the base, and through the gas permeable adhesive and
sheet.
[0241] As shown in FIGS. 22-23, lighting panels may be incorporated
into the base layer or the base layer may be a display screen of
the lighting panels.
[0242] As illustrated in FIG. 24, a build plate 700 for a
three-dimensional printer is shown. The build plate 700 includes an
optically transparent first channel layer 702, an optically
transparent, gas permeable second channel layer on the first
channel layer 704, and a flexible, optically transparent,
gas-permeable sheet 706 having an upper and lower surface. The
sheet upper surface forms a build surface 710 for forming a
three-dimensional object. Adhesive layers 712 and 714 are between
the channel layers 702 and 704, and between the channel layer 704
and the sheet 706, respectively. The channel layer 702 includes
channels 702A that are fluidly connected to a pressure controller
720, and the channel layer 704 includes channels 704A that are
fluidly connected to a gas source 760 on one side and a vacuum or
outlet 770 on the other side. As illustrated, the channel layer 704
includes a planar portion 704B with a bottom surface that is
adhered to the channel layer 702 by the adhesive layer 714 and a
top surface. The channel layer 704 also includes a channel-defining
portion 704C on the top surface of the planar portion 704B.
[0243] The sheet 706 may be formed of any suitable semipermeable or
permeable material (that is, permeable to the polymerization
inhibitor) including amorphous fluoropolymers as described herein.
For example, the polymer film or polymer film layer may, for
example, be a fluoropolymer film, such as an amorphous
thermoplastic fluoropolymer like TEFLON AF 1600.TM. or TEFLON AF
2400.TM. fluoropolymer films, or perfluoropolyether (PFPE),
particularly a crosslinked PFPE film, or a crosslinked silicone
polymer film The channel layer 704 may include a gas permeable or
semipermeable material, such as a permeable polymer (e.g.,
poly(dimethylsiloxane) (PDMS). The thickness of the sheet 706 may
be less than about 150 .mu.m. The planar portion 704B and the
channel-defining portion 704C may be adhered together by chemical
bonding including oxidative treatments, including oxygen plasma
treatments, UV ozone treatments and/or wet chemical treatments. The
adhesive layer 714 may be gas-permeable adhesives, such as a
poly(dimethylsiloxane) (PDMS) film. In this configuration, the gas
source 760 may increase the flow through the channels 704A to the
vacuum/outlet 770. The increased gas flow in the channels 704A may
increase the flow of gas through the channel layer 704, the
adhesive 712 and the sheet 706, which are gas permeable and may
increase the gas polymerization inhibitor present on the build
surface 710. For example, the gas source 760 may be an oxygen gas
source or other gas for inhibiting polymerization at the build
surface 710. Although the channels 702A and 704A are illustrated as
being parallel to one another, it should be understood that the
channels 702A and 704A may be generally orthogonal to one another
to improve optical qualities of the build plate 700.
[0244] The build plate 700 may be sufficiently thin and/or flexible
such that the build plate 700 may curve or bend. In some
embodiments, the build plate 700 has a thickness of between 10, 20,
30, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900 microns and 1,
2, 3, 4, 5, 6, 7, 8, 9 or 10 millimeters. In some embodiments, the
build plate 700 has a Young's modulus of about 70-80 GPa and/or a
Vickers Hardness of about 500-750 kgf/mm.sup.2.
[0245] In some embodiments, the pressure controller 750 may
increase or decrease the pressure in the channels 702A of the
channel layer 702 such that the build plate 700 may be flexed
upward (increased pressure) or downward (decreased pressure). The
pressure controller 750 may be connected to the channels 702A- by a
chamber that includes the channels 702A as discussed with respect
to FIG. 25 below. In some embodiments, the channels 702A may be
fluidly connected to one another, for example, by a connecting
channel or channels, such that a fluid connection between the
pressure controller 750 and any one of the channels 702A may be
sufficient to control the pressure in all of the channels 702A.
Accordingly, the pressure in the channels 702A may be controlled by
the pressure controller 750. As discussed above, the build plate
700 may be flexible. During the build, as the carrier/object moves
away from the build surface 710, the build plate 700 flexes in an
upward direction such as in the shape of a dome. As the build plate
700 continues to flex upward, the pressure controller 750 may
reduce the pressure in the channels 702A to exert a downward force
on the build plate 700 until the build plate 700 generally returns
to and is pulled back to a generally planar position. When the
build plate 700 returns to a planar position, the movement of the
build plate 700 may aid in pulling additional polymerizable liquid
(e.g., resin) into the build region under the object/carrier.
Accordingly, the oscillation of the build plate 700 may be
sufficient to enhance or speed a refilling of the build region with
polymerizable liquid. In addition, the pressure controller 750 may
increase the speed of oscillation and/or the force with which the
build plate 700 moves from a dome-shaped or flexed position to the
planar position, which may increase the flow of polymerizable
liquid into the build region on the build surface 710.
[0246] In some embodiments, the pressure controller 750 may be
capable of increasing and decreasing the pressure in the channels
702A above and below atmospheric pressure; however, the pressure
controller 750 may also be provided by a vacuum pump that reduces
pressure in the channels 702A, which exerts a reduced pressure on
the bottom of the build plate 700 to increase the speed of
oscillations and/or the force with which the build plate 700
returns from a position that is flexed upward to the planar
position.
[0247] As illustrated in FIG. 25, the build plate 700 may be held
in position to provide a build surface 710 for a three-dimensional
printer by a housing 800. As illustrated, the channel layer 702 is
wider than the other layers of the build plate 700 such that the
channel layer 702 is held under tension by a clamp in the housing
800. When the build plate 700 is in the housing 800, the housing
800 forms a lower chamber 802 that is fluidly connected to the
pressure controller 750 and an upper chamber 804 that is fluidly
connected to the gas source 760 and vacuum/outlet 770. The upper
and lower chambers 802 and 804 are separated by the channel layer
702. A sealing member 806, such as caulk or other sealing
materials, may be provided on the edges of the upper surface of the
build plate 700 at the intersection with the housing 800 to reduce
or prevent polymerizable fluid (e.g., resin) from entering the
chamber 804. A base 810 may be included in the lower chamber 802 to
provide additional planar support to the build plate 700. The base
810 may be formed of sapphire, glass, polymer and/or quartz and
positioned on a bottom surface of the channel layer 702.
[0248] In this configuration, the flow of a polymerization
inhibitor gas from the gas source 760 to the vacuum/outlet 770
through the channels 704 may be increased and/or the pressure of
the gas increased such that additional polymerization inhibitor
reaches the build surface 710. In addition, flexing of the build
plate 700 during the build may be controlled by the pressure
controller 750 such that oscillations may be controlled or
increased in frequency to increase the flow of polymerizable fluid
to the build surface 710. These features may increase a build speed
of a three-dimensional object due to an increased presence of a
polymerization inhibitor gas at the build surface and an increase
in oscillations to draw more polymerizable fluid to the build
surface 710.
[0249] The lighting panel 900 may be a lighting panel with
individually addressable radiation transmitting elements or pixels,
and the lighting panel may be controlled by a lighting panel
controller to form a desired lighting pattern on the build surface.
In some embodiments, the lighting panel is an LCD panel or OLED
panel. Plasma or CRT screens may also be used. The lighting panel
may be a monochromatic panel, such as a monochromatic or grayscale
LCD in which the sub-pixel color filters (R, G, and B) of a
traditional color LCD are removed to increase the light intensity
and increase build speed. The light source of the lighting panel
may include an LED array or other suitable light source and may
produce light in the ultraviolet range, such as about 300-450 nm or
about 400 nm. Although conventional LCD screens typically use white
light LEDs, in some embodiments the LED backlight source may be UV
LED's. Diffusers and color filters may also be used to permit
higher transmission of UV light in such a lighting panel.
[0250] Accordingly, the light panel light source may be integrated
into the build plate of the 3D printing device. In some
embodiments, lighting panel may irradiate the build surface as
light is directly or nearly directly projected to the build surface
substantially without magnification (e.g., with about a one-to-one
magnification ratio), which may provide increased resolution and
intensity of illumination as compared to projection systems.
[0251] In some embodiments, additional light guides may be added to
the build plate to increase resolution on the build surface. Light
guides or collimating structures, such as a micro-lens array or
honeycomb structure, may be used, in particular, in embodiments in
which an elastomeric layer or other layers are used to provide
additional compliance of the build plate at the build surface or
thicker build plates (e.g., greater than about 1-10 millimeters),
which may introduce light distortion. Light guides may be formed in
the build plate layer(s), such as in the elastomeric layer. For
example, light guides in the build plate may correspond to
individual pixels in the lighting panel to further guide light to
the build surface. Stated otherwise, individual light guides may be
formed in the build plate to align with pixels in the lighting
panel.
[0252] The lighting panels described herein may be used with any
suitable configuration of build plate. In some embodiments, the
lighting panels may be integrated with the build plate such that
the build plate bottom surface forms at least a portion of the
lighting panel display screen or the lighting panel screen is
affixed to the bottom surface of the build plate. Oxygen or other
polymerization inhibitor(s) may be provided to the build surface by
flow channels in the build plate as shown in FIGS. 22-25 or by
other flow structures or materials, such as mesh layers or
permeable layers. In some embodiments, a reduced pressure area may
be formed below the build plate. The reduced pressure area may be
greater on one side of the build plate and/or may oscillate in
order to potentially cause movement of the top surface(s) of the
build plate to increase resin flow to the build area and/or to
increase air/oxygen/polymerization inhibitor flow to the build
surface.
[0253] In some embodiments, heating/cooling elements may be used to
further control the build process. As an example, conductive
materials such as conductive nanoparticles may be used in one or
more layers (the permeable sheet, the adhesive, the permeable
channel layer, the elastomer layer and/or the base) to provide
active heating of the build plate. Heating of the build plate may
in turn heat the resin and reduce the viscosity of the resin. A
voltage may be applied to the conductive, transparent material to
drive a current, and the conductive material may function as a
resistive heater. See X. Gong, W. Wen, Polydimethylsiloxane-based
Conducting Composites and their Applications in Microfluidic Chip
Fabrication, Biomicrofluidics, 3, 012007 (2009) and U.S. Pat. No.
8,243,358, the disclosure of which is hereby incorporated by
reference in its entirety.
[0254] Although some embodiments are described with respect to the
build plates in FIGS. 22-25, lighting panels may be incorporated
into any suitable build plate (e.g., the build plate base may serve
as a screen of the lighting panel), or the lighting panels may be
provided as a separate unit underneath the build plate. Additional
examples of build plates may be found in U.S. Patent Publication
Nos. 2016/0200052 and 2016/0193786 and International Publication
Nos. WO2016/025579; WO2016/123506; and WO2016/123499, the
disclosures of which are hereby incorporated by reference in their
entireties.
[0255] The polymerization inhibitor gas may be supplied to the
polymerizable liquid through the optically transparent member in
various configurations as described herein.
[0256] The amount and duration of the reduced pressure applied to
the polymerizable liquid through the optically transparent member
is preferably sufficient to reduce a gas concentration in the
polymerizable liquid. The pressure may be at 0%, 5%, 10%, 20%, 25%,
30%, 40% to 50%, 60%, 70%, 80%, 90% or 100% of atmospheric
pressure.
[0257] In some embodiments, the polymerizable fluid has a gradient
of gas concentration, which determines an amount of irradiation or
"dose" to cure the polymerizable liquid. For example, the
polymerizable fluid can have a lower region on the optically
transparent member, and an upper region on the lower region
opposite the optically transparent member such that the lower
region has a higher dose to cure than the upper region. The applied
reduced pressure to the polymerizable liquid through the optically
transparent member may reduce a gas concentration in the upper
region, while maintaining the polymerization inhibitor gas in the
lower region, which consequently reduces a thickness of the dead
zone. In some embodiments, the thickness of the lower region is
less than about 1000 microns or between about 1, 2, 5, 10, 20 50,
100, 200 300 to 400, 500, 600, 700, 800, 900 or 1000 microns.
[0258] In some embodiments, oxygen gas may be used as the
polymerization inhibitor. Oxygen may be supplied at any suitable
pressure, and is preferably supplied at a pressure that is less
than atmospheric pressure. In particular embodiments, the pressure
of the oxygen is substantial equal to a partial pressure of oxygen
in air at atmospheric pressure. The polymerization inhibitor gas
may also be substantially devoid of nitrogen or other gases that do
not substantially contribute to polymerization inhibition in the
dead zone.
[0259] Without wishing to be bound by any particular theory, resins
that are saturated with gas are prone to degassing when the local
pressure drops. Large pressure drops can occur during the build
platform movement and resin refill. When the separation of the
printed part and window result in gas coalescence, voids may be
formed in the printed part. Accordingly, controlling the pressure
of a gas or applying a vacuum through the gas permeable build plate
may reduce the level of dissolved gases prior to the pressure
change, and reducing an amount of dissolved gas may increase the
pressure differential that the resin can experience prior to void
formation. The build plate is permeable to gasses, and equilibrium
may be established at the build plate/resin interface relatively
quickly. Cycling between air (or oxygen) and vacuum for printing
formation and part movement, respectively, may permit the CLIP
process to be performed with a maximum pressure differential on the
resin prior to void formation the part. Moreover, the removal of
nitrogen, which is not an active component of polymerization
inhibition, may reduce the overall gas level and further reduce the
formation of bubbles or voids in the printed part.
[0260] In addition, while oxygen delivery to the interface between
the polymerizable fluid and the build plate is desirable, oxygen in
the regions of the polymerization fluid that are further away from
the interface may lead to a larger dosage of irradiation to cure
the polymerizable fluid, which results in a longer exposure time
and slower print speeds. Reducing the overall oxygen level may lead
to faster cure times, by may lead to difficulty maintaining
sufficient oxygen at the interface for the CLIP process to be
effective. Moreover, since the light intensity decays as it passes
through the polyermization fluid, the percent monomer to polymer
conversions may not be constant throughout the exposed region.
Controlling a level of oxygen concentration may reduce exposure
times and increase print speeds by effectively maintaining a level
of oxygen at the build plate and polymerization fluid interface.
The oxygen concentration profile may also be controlled to provide
more consistent percent monomer to polymer conversions in view of
variations of light intensity.
[0261] While the present invention has been described in connection
with polymerizable liquids, those skilled in the art will
appreciate that the methods and apparatus described herein may be
used with any suitable solidifiable liquid, including organic and
inorganic materials. In some embodiments, "dual cure" polymerizable
liquids (or "resins"), and methods that may be used in carrying out
the present invention include, but are not limited to, those set
forth in J. Rolland et al., Method of Producing Polyurethane
Three-Dimensional Objects from Materials having Multiple Mechanisms
of Hardening, PCT Publication No. WO 2015/200179 (published 30 Dec.
2015); J. Rolland et al., Methods of Producing Three-Dimensional
Objects from Materials Having Multiple Mechanisms of Hardening, PCT
Publication No. WO 2015/200173 (published 30 Dec. 2015); J. Rolland
et al., Three-Dimensional Objects Produced from Materials Having
Multiple Mechanisms of Hardening, PCT Publication No.
WO/2015/200189 (published 30 Dec. 2015); J. Rolland et al.,
Polyurethane Resins Having Multiple Mechanisms of Hardening for Use
in Producing Three-Dimensional Dimensional Objects published 30
Dec. 2015); and J. Rolland et al., Method of Producing
Three-Dimensional Objects from Materials having Multiple Mechanisms
of Hardening, U.S. patent application Ser. No. 14/977,822 (filed 22
Dec. 2015); J. Rolland et al., Method of Producing Polyurethane
Three-Dimensional Objects from Materials having Multiple Mechanisms
of Hardening, U.S. patent application Ser. No. 14/977,876 (filed 22
Dec. 2015), J. Rolland et al., Three-Dimensional Objects Produced
from Materials having Multiple Mechanisms of Hardening, U.S. patent
application Ser. No. 14/977,938 (filed 22 Dec. 2015), and J.
Rolland et al., Polyurethane Resins having Multiple Mechanisms of
Hardening for Use in Producing Three-Dimensional Objects, U.S.
patent application Ser. No. 14/977,974 (filed 22 Dec. 2015); the
disclosures of all of which are incorporated by reference herein in
their entirety.
[0262] While the present invention is preferably carried out by
continuous liquid interphase polymerization, as described in detail
above, in some embodiments alternate methods and apparatus for
bottom-up three-dimension fabrication may be used, including
layer-by-layer fabrication. Examples of such methods and apparatus
include, but are not limited to, those described U.S. Pat. No.
7,438,846 to John and U.S. Pat. No. 8,110,135 to El-Siblani, and in
U.S. Patent Application Publication Nos. 2013/0292862 to Joyce and
2013/0295212 to Chen et al. The disclosures of these patents and
applications are incorporated by reference herein in their
entirety.
[0263] The present invention is explained in greater detail in the
following non-limiting Examples.
EXAMPLE 1
Continuous Fabrication with Intermittent Irradiation and
Advancing
[0264] A process of the present invention is illustrated in FIG. 6,
where the vertical axis illustrates the movement of the carrier
away from the build surface. In this embodiment, the vertical
movement or advancing step (which can be achieved by driving either
the carrier or the build surface, preferably the carrier), is
continuous and unidirectional, and the irradiating step is carried
out continuously. Polymerization of the article being fabricated
occurs from a gradient of polymerization or active surface, and
hence creation of "layer by layer" fault lines within the article
is minimized.
[0265] An alternate embodiment of the present invention is
illustrated in FIG. 7. In this embodiment, the advancing step is
carried out in a step-by-step manner, with pauses introduced
between active advancing of the carrier and build surface away from
one another. In addition, the irradiating step is carried out
intermittently, in this case during the pauses in the advancing
step. We find that, as long as the inhibitor of polymerization is
supplied to the dead zone in an amount sufficient to maintain the
dead zone and the adjacent gradient of polymerization or active
surface during the pauses in irradiation and/or advancing, the
gradient of polymerization is maintained, and the formation of
layers within the article of manufacture is minimized or avoided.
Stated differently, the polymerization is continuous, even though
the irradiating and advancing steps are not. Sufficient inhibitor
can be supplied by any of a variety of techniques, including but
not limited to: utilizing a transparent member that is sufficiently
permeable to the inhibitor, enriching the inhibitor (e.g., feeding
the inhibitor from an inhibitor-enriched and/or pressurized
atmosphere), etc. In general, the more rapid the fabrication of the
three-dimensional object (that is, the more rapid the cumulative
rate of advancing), the more inhibitor will be required to maintain
the dead zone and the adjacent gradient of polymerization.
EXAMPLE 2
[0266] Continuous Fabrication with Reciprocation During Advancing
to Enhance Filling of Build Region with Polymerizable Liquid
[0267] A still further embodiment of the present invention is
illustrated in FIG. 8. As in Example 10 above, this embodiment, the
advancing step is carried out in a step-by-step manner, with pauses
introduced between active advancing of the carrier and build
surface away from one another. Also as in Example 1 above, the
irradiating step is carried out intermittently, again during the
pauses in the advancing step. In this example, however, the ability
to maintain the dead zone and gradient of polymerization during the
pauses in advancing and irradiating is taken advantage of by
introducing a vertical reciprocation during the pauses in
irradiation.
[0268] We find that vertical reciprocation (driving the carrier and
build surface away from and then back towards one another),
particularly during pauses in irradiation, serves to enhance the
filling of the build region with the polymerizable liquid,
apparently by pulling polymerizable liquid into the build region.
This is advantageous when larger areas are irradiated or larger
parts are fabricated, and filling the central portion of the build
region may be rate-limiting to an otherwise rapid fabrication.
[0269] Reciprocation in the vertical or Z axis can be carried out
at any suitable speed in both directions (and the speed need not be
the same in both directions), although it is preferred that the
speed when reciprocating away is insufficient to cause the
formation of gas bubbles in the build region.
[0270] While a single cycle of reciprocation is shown during each
pause in irradiation in FIG. 8, it will be appreciated that
multiple cycles (which may be the same as or different from one
another) may be introduced during each pause.
[0271] As in Example 1 above, as long as the inhibitor of
polymerization is supplied to the dead zone in an amount sufficient
to maintain the dead zone and the adjacent gradient of
polymerization during the reciprocation, the gradient of
polymerization is maintained, the formation of layers within the
article of manufacture is minimized or avoided, and the
polymerization/fabrication remains continuous, even though the
irradiating and advancing steps are not.
EXAMPLE 3
Acceleration During Reciprocation Upstroke and Deceleration During
Reciprocation Downstroke to Enhance Part Quality
[0272] We observe that there is a limiting speed of upstroke, and
corresponding downstroke, which if exceeded causes a deterioration
of quality of the part or object being fabricated (possibly due to
degradation of soft regions within the gradient of polymerization
caused by lateral shear forces a resin flow). To reduce these shear
forces and/or enhance the quality of the part being fabricated, we
introduce variable rates within the upstroke and downstroke, with
gradual acceleration occurring during the upstroke and gradual
deceleration occurring during the downstroke, as schematically
illustrated in FIG. 9.
EXAMPLE 4
Fabrication in Multiple Zones
[0273] FIG. 10 schematically illustrates the movement of the
carrier (z) over time (t) in the course of fabricating a
three-dimensional object by methods as described above, through a
first base (or "adhesion") zone, an optional second transition
zone, and a third body zone. The overall process of forming the
three-dimensional object is thus divided into three (or two)
immediately sequential segments or zones. The zones are preferably
carried out in a continuous sequence without pause substantial
delay (e.g., greater than 5 or 10 seconds) between the three zones,
preferably so that the gradient of polymerization is not disrupted
between the zones.
[0274] The first base (or "adhesion") zone includes an initial
light or irradiation exposure at a higher dose (longer duration
and/or greater intensity) than used in the subsequent transition
and/or body zones. This is to obviate the problem of the carrier
not being perfectly aligned with the build surface, and/or the
problem of variation in the positioning of the carrier from the
build surface, at the start of the process, by insuring that the
resin is securely polymerized to the carrier. Note an optional
reciprocation step (for initial distributing or pumping of the
polymerizable liquid in or into the build region) is shown before
the carrier is positioned in its initial, start, position. Note
that a release layer (not shown) such as a soluble release layer
may still be included between the carrier and the initial
polymerized material, if desired. In general, a small or minor
portion of the three-dimensional object is produced during this
base zone (e.g., less than 1, 2 or 5 percent by volume). Similarly,
the duration of this base zone is, in general, a small or minor
portion of the sum of the durations of the base zone, the optional
transition zone, and the body zone (e.g., less than 1, 2 or 5
percent).
[0275] Immediately following the first base zone of the process,
there is optionally (but preferably) a transition zone. In this
embodiment, the duration and/or intensity of the illumination is
less, and the displacement of the oscillatory step less, compared
to that employed in the base zone as described above. The
transition zone may (in the illustrated embodiment) proceed through
from 2 or 5, up to 50 or more oscillatory steps and their
corresponding illuminations. In general, an intermediate portion
(greater than that formed during the base zone, but less than that
formed of during the body zone), of the three dimensional object is
produced during the transition zone (e.g., from 1, 2 or 5 percent
to 10, 20 or 40 percent by volume). Similarly, the duration of this
transition zone is, in general, greater than that of the base zone,
but less than that of the body zone (e.g., a duration of from 1, 2
or 5 percent to 10, 20 or 40 percent that of the sum of the
durations of the base zone, the transition zone, and the body zone
(e.g., less than 1, 2 or 5 percent).
[0276] Immediately following the transition zone of the process
(or, if no transition zone is included, immediately following the
base zone of the process), there is a body zone, during which the
remainder of the three-dimensional object is formed. In the
illustrated embodiment, the body zone is carried out with
illumination at a lower dose than the base zone (and, if present,
preferably at a lower dose than that in the transition zone), and
the reciprocation steps are (optionally but in some embodiments
preferably) carried out at a smaller displacement than that in the
base zone (and, if present, optionally but preferably at a lower
displacement than in the transition zone). In general, a major
portion, typically greater than 60, 80, or 90 percent by volume, of
the three-dimensional object is produced during the transition
zone. Similarly, the duration of this body zone is, in general,
greater than that of the base zone and/or transition zone (e.g., a
duration of at least 60, 80, or 90 percent that of the sum of the
durations of the base zone, the transition zone, and the body
zone). Note that, in this example, the multiple zones are
illustrated in connection with an oscillating mode of fabrication,
but the multiple zone fabrication technique described herein may
also be implemented with other modes of fabrication as illustrated
further in the examples below (with the transition zone illustrated
as included, but again being optional).
EXAMPLE 5
Fabrication with Intermittent (or "Strobe") Illumination
[0277] The purpose of a "strobe" mode of operation is to reduce the
amount of time that the light or radiation source is on or active
(e.g., to not more than 80, 70, 60, 50, 40, or 30 percent of the
total time required to complete the fabrication of the
three-dimensional object), and increase the intensity thereof (as
compared to the intensity required when advancing is carried out at
the same cumulative rate of speed without such reduced time of
active illumination or radiation), so that the overall dosage of
light or radiation otherwise remains substantially the same. This
allows more time for resin to flow into the build region without
trying to cure it at the same time. The strobe mode technique can
be applied to any of the existing general modes of operation
described herein above, including continuous, stepped, and
oscillatory modes, as discussed further below.
[0278] FIG. 11A schematically illustrates one embodiment of
continuous mode. In the conventional continuous mode, an image is
projected and the carrier starts to move upwards. The image is
changed at intervals to represent the cross section of the
three-dimensional object being produced corresponding to the height
of the build platform. The speed of the motion of the build
platform can vary for a number of reasons. As illustrated, often
there is a base zone where the primary goal is to adhere the object
to the build platform, a body zone which has a speed which is
suitable for the whole object being produced, and a transition zone
which is a gradual transition from the speed and/or dosages of the
base zone to the speeds and/or dosages of the body zone. Note that
cure is still carried out so that a gradient of polymerization,
which prevents the formation of layer-by-layer fault lines, in the
polymerizable liquid in the build region, is preferably retained,
and with the carrier (or growing object) remaining in liquid
contact with the polymerizable liquid, as discussed above.
[0279] FIG. 11B schematically illustrates one embodiment of strobe
continuous mode. In strobe continuous the light intensity is
increased but the image is projected in short flashes or
intermittent segments. The increased intensity allows the resin to
cure more quickly so that the amount of flow during cure is minimal
The time between flashes lets resin flow without being cured at the
same time. This can reduce problems caused by trying to cure moving
resin, such as pitting.
[0280] In addition, the reduced duty cycle on the light source
which is achieved in strobe mode can allow for use of increased
intermittent power. For example: If the intensity for the
conventional continuous mode was 5 mW/cm.sup.2 the intensity could
be doubled to 10 mW/cm.sup.2 and the time that the image is
projected could be reduced to half of the time, or the intensity
could be increased 5-fold to 25 mW/cm.sup.2 and the time could be
reduced to 1/5.sup.th of the previous light on time.
[0281] FIG. 12A schematically illustrates one embodiment of stepped
mode: In the conventional stepped mode an image is projected while
the build platform is stationary (or moving slowly as compared to
more rapid movement in between illumination). When one height
increment is sufficiently exposed the image is turned off and the
build platform is moved upwards by some increment. This motion can
be at one speed or the speed can vary such as by accelerating from
a slow speed when the thickness of uncured resin is thin to faster
as the thickness of the uncured resin is thicker. Once the build
platform is in the new position the image of the next cross section
is projected to sufficiently expose the next height increment.
[0282] FIG. 12B schematically illustrates one embodiment of strobe
stepped mode: In the strobe stepped mode the light intensity is
increased and the amount of time that the image is projected is
reduced. This allows more time for resin flow so the overall speed
of the print can be reduced or the speed of movement can be
reduced. For example: If the intensity for the conventional stepped
mode was 5 mW/cm.sup.2 and the build platform moves in increments
of 100 um in 1 second and the image is projected for 1 second the
intensity could be doubled to 10 mW/cm.sup.2, the time that the
image is projected could be reduced to 0.5 seconds, and the speed
of movement could be reduced to 50 um/second, or the time that the
stage is moving could be reduced to 0.5 seconds. The increased
intensity could be as much as 5 fold or more allowing the time
allotted for image projection to be reduced to 1/5.sup.th or
less.
[0283] FIG. 13A schematically illustrates one embodiment of
oscillatory mode: In the oscillatory mode an image is again
projected while the build platform is stationary (or moving slowly
as compared to more rapid movement in-between illuminations). When
one height increment is cured the image is turned off and the build
platform is moved upwards to pull additional resin into the build
zone and then moved back down to the next height increment above
the last cured height. This motion can be at one speed or the speed
can vary such as by accelerating from a slow speed when the
thickness of uncured resin is thin to faster as the thickness of
the uncured resin is thicker. Once the build platform is in the new
position the image of the next cross section is projected to cure
the next height increment.
[0284] FIG. 13B illustrates one embodiment of strobe oscillatory
mode. In the strobe oscillatory mode the light intensity is
increased and the amount of time that the image is projected is
reduced. This allows more time for resin flow so the overall speed
of the print can be reduced or the speed of movement can be
reduced. For example: If the intensity for the conventional
oscillatory mode was 5 mW/cm.sup.2 and the build platform moves up
by 1 mm and back down to an increment of 100 um above the previous
height in 1 second and the image is projected for 1 second the
intensity could be doubled to 10 mW/cm.sup.2, the time that the
image is projected could be reduced to 0.5 seconds, and the speed
of movement could be reduced to by half or the time that the stage
is moving could be reduced to 0.5 seconds. The increased intensity
could be as much as 5 fold or more allowing the time allotted for
image projection to be reduced to 1/5.sup.th or less. Segment "A"
of FIG. 13 is discussed further below.
[0285] FIG. 14A illustrates a segment of a fabrication method
operated in another embodiment of strobe oscillatory mode. In this
embodiment, the duration of the segment during which the carrier is
static is shortened to close that of the duration of the strobe
illumination, so that the duration of the oscillatory segment
may--if desired--be lengthened without changing the cumulative rate
of advance and the speed of fabrication.
[0286] FIG. 14B illustrates a segment of another embodiment of
strobe oscillatory mode, similar to that of FIG. 14A, except that
the carrier is now advancing during the illumination segment
(relatively slowly, as compared to the upstroke of the oscillatory
segment).
EXAMPLE 6
Varying of Process Parameters During Fabrication
[0287] In the methods of the Examples above, the operating
conditions during the body zone are shown as constant throughout
that zone. However, various parameters can be altered or modified
in the course of the body zone or segment, as discussed further
below.
[0288] A primary reason for altering a parameter during production
would be variations in the cross section geometry of the
three-dimensional object; that is, smaller (easier to fill), and
larger (harder to fill) segments or portions of the same
three-dimensional object. For easier to fill segments (e.g., 1-5 mm
diameter equivalents), the speed of upwards movement could be quick
(up to 50-1000 m/hr) and/or the pump height could be minimal (e.g.,
as little at 100 to 300 um). For larger cross sectional segments
(e.g., 5-500 mm diameter equivalents) the speed of upward movement
can be slower (e.g., 1-50 mm/hr) and/or the pump height can be
larger (e.g., 500 to 5000 um). Particular parameters will, of
course, vary depending on factors such as illumination intensity,
the particular polymerizable liquid (including constituents thereof
such as dye and filler concentrations), the particular build
surface employed, etc.
[0289] In some embodiments, the overall light dosage (determined by
time and intensity) may be reduced as the "bulk" of the cross
section being illuminated increases. Said another way, small points
of light may need higher per unit dosage than larger areas of
light. Without wishing to be bound to any specific theory, this may
relate to the chemical kinematics of the polymerizable liquid. This
effect could cause us to increase the overall light dosage for
smaller cross sectional diameter equivalents.
[0290] In some embodiments, vary the thickness of each height
increment between steps or pumps can be varied. This could be to
increase speed with decreased resolution requirements (that is,
fabricating a portion that requires less precision or permits more
variability, versus a portion of the object that requires greater
precision or requires more precise or narrow tolerances). For
example, one could change from 100 um increments to 200 um or 400
um increments and group all the curing for the increased thickness
into one time period. This time period may be shorter, the same or
longer than the combined time for the equivalent smaller
increments.
[0291] In some embodiments, the light dosage (time and/or
intensity) delivered could be varied in particular cross sections
(vertical regions of the object) or even in different areas within
the same cross section or vertical region. This could be to vary
the stiffness or density of particular geometries. This can, for
example, be achieved by changing the dosage at different height
increments, or changing the grayscale percentage of different zones
of each height increment illumination.
[0292] Examples of body portion fabrication through multiple zones
are given in FIGS. 15A-19.
[0293] FIG. 15A is a schematic illustration of the fabrication of a
three-dimensional object similar to FIG. 13A, except that the body
segment is fabricated in two contiguous segments, with the first
segment carried out in an oscillatory operating mode, and the
second segment carried out in a continuous operating mode. FIG. 16A
is a schematic illustration of the fabrication of a
three-dimensional object similar to FIG. 11A, except that the body
segment is fabricated in three contiguous segments, with the first
and third segments carried out in a continuous operating mode, and
the second segment carried out in oscillatory operating mode. FIG.
17A is a schematic illustration of the fabrication of a
three-dimensional object similar to FIG. 16A, except that the base
zone, transition zone, and first segment of the body zone are
carried out in a strobe continuous operating mode, the second
segment of the body zone is fabricated in an oscillatory operating
mode, and the third segment of the body zone is fabricated in a
continuous operating mode.
[0294] FIG. 15B, 16B, and 17B are similar to the foregoing, except
that stepped or step-wise mode is used in place of oscillatory, or
"reciprocal" mode. In general, reciprocal or oscillatory mode is
preferred over stepped mode, with reciprocation being achieved
entirely through motion of the carrier, or the combined motion of
the carrier and a flexible, or movable, build surface.
[0295] FIG. 18A is a schematic illustration of the fabrication of a
three-dimensional object similar to FIG. 11A, except that light
intensity is varied in the course of fabricating the base and
transition zones, and both light intensity and rate of advancing
are varied in the course of fabricating the body zone. FIG. 18B is
a schematic illustration of the fabrication of a three-dimensional
object similar to FIG. 17A, except that light is interrupted in an
intermittent fashion (dashed line representing light intensity
during interrupted segments is for comparison to FIG. 17A
only).
[0296] FIG. 19 is a schematic illustration of the fabrication of a
three-dimensional object similar to FIG. 11A, except that the mode
of operation during fabrication of the body segment is changed
multiple times for continuous, to reciprocal, and back. This may be
employed not only to accommodate changes in geometry of the
three-dimensional object during fabrication, but a relatively
constant geometry where the part is hollow, to facilitate
replenishment of polymerizable liquid in the build region.
[0297] FIG. 20 schematically illustrates parameters that may be
varied within a reciprocal (also referred to as "oscillatory")
operating mode (solid line throughout) or a step operating mode
(solid line horizontal lines and dashed lines). Note the parameters
that may be varied in these two modes are similar, except for the
absence of a pump height parameter in step mode.
EXAMPLE 7
Varying of Slice Thickness During Fabrication
[0298] In the methods of the present invention, slice thickness may
be held constant or varied in any of the operating modes. Examples
are given in FIGS. 21A to 21F, where horizontal dashed lines
represent the transition from each contiguous slice (corresponding
to different exposure or illumination frames or patterns) during
the formation of the three-dimensional object.
[0299] FIG. 21A schematically illustrates a method of the invention
carried out in a continuous operating mode, with constant slice
thickness and constant carrier speed, while FIG. 21B schematically
illustrates a method of the invention carried out in a continuous
operating mode, with variable slice thickness with constant carrier
speed. In both cases, illumination or exposure is continuous, with
slices changing over time. Slice thickness could likewise be varied
in an intermittent exposure mode of operation (including strobe
mode).
[0300] FIG. 21C schematically illustrates a method of the invention
carried out in a continuous operating mode, with constant slice
thickness and variable carrier speed, while FIG. 21D schematically
illustrates a method of the invention carried out in continuous
operating mode, mode with variable slice thickness and variable
carrier speed. Again in both cases, illumination or exposure is
continuous with the slices changing over time, but slice thickness
could likewise be varied in an intermittent exposure mode of
operation.
[0301] FIG. 21E schematically illustrates a method of the invention
carried out in reciprocal operating mode, with constant slice
thickness, while FIG. 21F schematically illustrates a method of the
invention carried out in reciprocal operating mode, with variable
slice thickness. Bold diagonal hash patterns during the exposure
periods are to emphasize slice thickness, and variability thereof
in FIG. 21F. In both cases, a step-wise mode of operation could be
used in place of a reciprocal mode of operation (see, for example,
FIG. 20).
[0302] The foregoing is illustrative of the present invention, and
is not to be construed as limiting thereof. The invention is
defined by the following claims, with equivalents of the claims to
be included therein.
[0303] The foregoing is illustrative of the present invention, and
is not to be construed as limiting thereof. The invention is
defined by the following claims, with equivalents of the claims to
be included therein.
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